a perplexing paradox…

The case.

a 70 year old female is bought to your ED at 10pm via ambulance with a dense left-sided hemiparesis following a witnessed collapse at home only 30 minutes earlier.

She had apparently been well during the day and was seen to collapse to the ground whilst taking the rubbish outside after dinner. Her next-door neighbour states that the patient was alert but unable to communicate immediately after the event.

Her past medical history is significant for:

  • T2DM (on insulin)
  • HTN
  • Heavy smoker

Upon arrival to the department the patient looks unwell. She is pale and incredibly diaphoretic… 

On examination:

  • P 104/min (sinus), BP 70 systolic, SaO2 70% (15L NRB mask), RR 34, Temp 36.4*C
  • Chest clear to auscultation
  • HS dual. No murmurs, rubs or gallop.
  • Abdomen soft & non-tender without palpable pulsatile masses.
  • GCS 10/15 (E4, V1, M5) with obvious left-sided facial droop & dense (0/5) hemiparesis.
  • No peripheral oedema. Peripheral pulses present. No limb swelling.

You pause for a moment and think…

Collapse & hemiparesis 

  • ? Ischaemic stroke
  • ? Intracranial haemorrhage (including SAH, AVM)
  • ? Seizure with Todds paresis

But she’s terribly diaphoretic!!

  • ? Hypoglycaemia (can cause focal neurology and is considered a stroke mimic)

But how do you explain the hypoxia or the shock??

  • ? Myocardial infarction
  • ? Aortic dissection
  • ? Dysrhythmia
  • ? Acute valvular pathology / AAA rupture

But her chest is clear!!

  • ? Pulmonary embolism

With such a diverse list of potential diagnoses, you commence resuscitation and continue your investigations…..

  • BSL 8.4mmol/L
  • ECG: no STEMI or evidence of ischaemia
  • CXR:

Perplexing paradox CXR

During the first 15 minutes in the Emergency Department her treatment includes;

  • 2x IV access
  • Fluid bolus – 1L 0.9% Saline
  • Arterial line is placed
  • Peripheral adrenaline infusion commenced & rapidly titrated to 20mcg/min
  • Pre-oxygenation whilst the team set up for rapid-sequence intubation

  • No pericardial effusion
  • No PTx or intraperitoneal fluid.
  • No AAA
  • A large right ventricle is noted
  • Her IVC is distended and non-collapsing

Following an uneventful RSI, she remains hypoxic and shocked.

Her observations are now…

  • Pulse 110
  • BP 76/50 – now on 30mcg/min of adrenaline
  • SaO2 94% on FiO2 1.0 & PEEP 8cmH2O

This is her blood gas…

Perplexing paradox ABG

Severe hypoxaemia with an Aa gradient >500

You are now faced with a challenging scenario…

This critically ill lady has features of a simultaneous acute stroke plus massive pulmonary embolism !!

She is too sick to move from your resuscitation bay and you do not consider it safe to transfer her to radiology for advanced imaging.

Given this challenging clinical snookering you decide to administer empiric intravenous thrombolysis (alteplase) based on the likelihood that this is most likely a thrombotic aetiology.

Within 10 minutes of your bolus dose her haemodynamics normalise and you are able to wean the vasopressor infusion back to 5 mcg/min. Her oxygen requirement also subsequently falls…

CT Brain.

There is a hyperdense left MCA (at M1/M2 junction) consistent with acute thrombosis. There is acute infarct involving the insular cortex and frontal operculum.

Perplexing Paradox CTB


Multiple segmental and subsegmental pulmonary emboli demonstrated bilaterally. There is minor reflux of contrast into the IVC and the right ventricle is prominent in keeping with a degree of right heart strain.

Perplexing Paradox CTPA

Paradoxical Embolism

The basics.

Paradoxical embolism refers to the clinical phenomenon of thromboembolism originating in the venous vasculature which traverses through an intracardiac or pulmonary shunt into the systemic circulation.

Paradoxical embolisms have been documented in medical literature as far back as 1877. These result from a venous thromboembolism that transits from the right- to the left-sided cardiac chambers. They may occur via interventricular or interatrial defects, or via pulmonary arteriovenous malformations.

Of the 500,000+ strokes per annum in the United States, a cause remains unidentified or unproven in 40-45% of cases despite comprehensive diagnostic workups. These strokes are known as cryptogenic strokes. The most common cause of cryptogenic stroke is probably paradoxical embolism due to a patent foramen ovale (PFO).

Patent foramen ovale.

Normal foetal circulation is dependent on the foramen ovale, which provides a communication for oxygenated blood flow between the right atrial and left atrial during lung maturation. At birth, decreased pulmonary vascular resistance and increased left atrial pressure promote closure of the foramen ovale.

Patent Foramen Ovale. Image courtesy of clevelandclinic.org

Patent Foramen Ovale.
Image courtesy of clevelandclinic.org

Whilst PFO’s are found in ~27% of the general population, their incidence is much higher (OR 2.9) in patients with cryptogenic stroke. The annual risk of cryptogenic and recurrent stroke in PFO populations is 0.1% and 1%, respectively.


The precise mechanism of stroke in patients with a PFO is unresolved. Under physiological conditions, a pressure gradient is maintained between the left and right atrium, which results in passive closure of the PFO. In the case of increased right atrial pressure exceeding left atrial pressure (as observed at the end of Valsalva manoeuvres such as coughing, sneezing or squatting) a transient right-to-left shunt may occur carrying particulate matter such as thrombi into the systemic circulation. A permanent increase in right-sided cardiac pressures, as observed after pulmonary embolism or other causes of pulmonary arterial hypertension, results in a significant and possibly permanent right-to-left interatrial shunt, thereby increasing the risk for paradoxical embolism.

Clinical features.

The clinical diagnosis of paradoxical embolism requires a venous source of embolism, an intracardiac defect or a pulmonary fistula and evidence of arterial embolism.

Depending on the site of embolisation, paradoxical embolism may result in neurological deficits related to ischaemic stroke, chest pain and ECG changes indicative of myocardial infarction, acute abdominal pain from mesenteric ischaemia, back pain and haematuria as a result of renal infarction, or cold and pulseless extremities secondary to peripheral arterial occlusion.

Paradoxical Embolism: Pathophysiology, Diagnostic Tools, and Prevention Image courtesy of J Am Coll Cardiol. 2014;64(4):403-415.

Making the diagnosis.

The formal diagnostic evaluation required in patients with cryptogenic stroke will far exceed any Emergency Department length of stay. However, in patients with cryptogenic embolism and a coexisting intracardiac communication at the atrial level, the presumptive diagnosis of paradoxical embolism should be seriously entertained.


Transthoracic or transoesophageal echocardiography are the diagnostic method of choice for the noninvasive detection of intracardiac shunts and a patent ductus arteriosus. It also allows clinicians to assess the size of a defect and provides information on shunt quantity and direction.

The “bubble study”.
Accurate PFO detection requires peripheral injection of agitated saline or echocardiographic contrast medium at the end of a sustained and rigorous Valsalva manoeuver. The echo criteria for PFO diagnosis include the early detection of contrast microbubbles in the left atrium within 3 cardiac cycles after opacification of the right atrium (see below).

Transthoracic echocardiography showing contrast medium passing through the patent foramen ovale. Courtesy of Rev Esp Cardiol. 2011;64:133-9.

Transthoracic echocardiography showing contrast medium passing through the patent foramen ovale.
Image courtesy of Rev Esp Cardiol. 2011;64:133-9.

Transoesophageal echo (TOE) is considered to be the “gold standard” technique for the diagnosis of right-to-left shunts, however the use of sedation to facilitate the study often reduces the performance of Valsalva manoeuver. Keep in mind however that the sensitivity of transthoracic echo (TTE) may be as low as 63%.
Other imaging techniques.

These include transcranial doppler sonography, computed tomography and cardiac MRI.



Antiplatelet therapy (aspirin, clopidogrel or a dipyridamole) is first-line in the secondary prevention of systemic paradoxical embolism. Further anticoagulation with heparin, LMWH, warfarin or rivaroxaban etc is indicated for cardioembolic disease and in the presence of concomitant pulmonary embolism.


Percutaneous closure of cardiac septal defects is frequently performed however evidence supporting this practice is inconclusive when compared to medical therapy alone.

The patient is transferred to the intensive care unit on minimal vasopressor support.

24 hours into her admission she has a formal transthoracic echo (whilst still intubated and sedated) which demonstrates normal LV and RV size and systolic function. Her pulmonary pressures are normal and there is no evidence of intracardiac shunt on a bubble study.

A cause was never found for her paradoxical embolism, but one is left to ponder whether the acute pulmonary hypertension caused by a massive pulmonary embolism was enough to drive a transient right-to-left shunt resulting in her subsequent ischaemic stroke.

  1. Windecker, S., Stortecky, S., & Meier, B. (2014). Paradoxical embolism. Journal of the American College of Cardiology, 64(4), 403–415. http://doi.org/10.1016/j.jacc.2014.04.063
  2. Maron, B. A., Shekar, P. S., & Goldhaber, S. Z. (2010). Paradoxical embolism. Circulation, 122(19), 1968–1972. http://doi.org/10.1161/CIRCULATIONAHA.110.961920
  3. Poole-Wilson, P. A., May, A. R., & Taube, D. (1976). Paradoxical embolism complicating massive pulmonary embolus. Thorax, 31(3), 354–355.
  4. Pinto, F. J. (2005). When and how to diagnose patent foramen ovale. Heart, 91(4), 438–440. http://doi.org/10.1136/hrt.2004.052233
  5. Naidoo, P., & Hift, R. (2011). Massive pulmonary thromboembolism and stroke. Case Reports in Medicine, 2011, 398571. http://doi.org/10.1155/2011/398571
  6. d’audiffret, A., Pillai, L., & Dryjski, M. (1999). Paradoxical emboli: the relationship between patent foramen ovale, deep vein thrombosis and ischaemic stroke. European Journal of Vascular and Endovascular Surgery : the Official Journal of the European Society for Vascular Surgery, 17(6), 468–471. http://doi.org/10.1053/ejvs.1999.0776

twist and shout….

the case.

34 year old female presents to ED with a 2 day history of worsening left-sided pleuritic chest pain associated with shortness of breath. There has been no associated cough, fever or sputum production.

She is one week post-Caesarian section; an uncomplicated, elective procedure from which she has recovered well.


  • prior LCSC (5 years ago)
  • Splenomegaly (?cause)
  • No regular medications
  • Penicillin allergy

On examination.
Alert but distressed in pain, able to speak in full sentences.
P 102, BP 126/70, RR 22, SaO2 99% (on air).
Heart sounds dual without rub or murmur.
Chest: Clear without crackles/wheeze. No pleural rub. Non-tender chest wall without rashes or vesicles.
Abdomen: Soft & NT with palpable spleen. Appropriately healing Caesarian scar.
No unilateral calf swelling or pitting oedema.

  • Pulmonary embolism
  • Pneumonia
  • Pneumothorax
  • Pleural effusion ?cause
  • Subphrenic pathology (including post-operative collection)
  • ….other ??

  • Hb 108, WCC 11.2, PLT 460
  • EUC/LFTs normal
  • ECG: Sinus tachycardia without features of right heart strain or myocardial ischaemia

Her is her CXR…

Twisting & Turning CXR

PA CXR with clear lung fields & normal cardiac silhouette. Costophrenic recess is preserved

Given the high pretest probability for PE and the lack of an obvious alternate diagnosis, you elect to proceed straight to advanced imaging and send your patient for a CTPA.

Here is her scan…


  • Suboptimal study; however no pulmonary embolism is demonstrated.
  • There is mild dependent atelectasis, worse on left.
  • The spleen is enlarged and its hilum faces laterally with varices. It also appears to sit inferiorly to its normal position (under the stomach & liver, and does not contact the diaphragm). It does not demonstrate its normal mottled appearance on the arterial phase.

Following a period of observation and titrated analgesia our patient settled and her observations normalised.

She was soon keen to go home and keep her newborn out of hospital. She was subsequently discharged with return precautions and a plan to followup with her GP the next morning.

The consultant radiologist has reviewed the images and amended the report.

It now reads;
” The spleen is enlarged and it is also rotated. It does not enhance normally and there is mild surrounding stranding. The splenic artery cannot be followed completely to the hilum. These findings are suspicious for splenic torsion.”

The patient is called back to the department and the diagnosis explained. She is admitted under the care of the surgeons and she undergoes further advanced imaging….

Arterial phase, axial CT of the abdomen. Red arrow demonstrating the laterally displaced splenic hilum.

Arterial phase, axial CT of the abdomen. Red arrow demonstrating the laterally displaced splenic hilum.


There are multiple case reports of spontaneous splenic torsion, typically relating to “a wandering spleen“.

What is a wandering spleen?

It is a rare condition characterised by the abnormal location of the spleen in the lower abdomen or pelvis. This results from increased splenic mobility due to the absence or laxity of its suspensory ligaments.

Wandering spleen has been described in patients ranging from 3 months to 82 years of age. It has an incidence of <0.25% of all splenectomies.


The causes of wandering spleen can be both congenital and acquired, with acquired risk factors including pregnancy, trauma & splenomegaly.

It can occur in all age groups, but classically occurs in 20-40 year old females. There are multiple case reports of splenic infarction occurring in postpartum women.


A wandering spleen may present clinically as an acute surgical abdomen secondary to torsion of the spleen around its vascular pedicle. This subsequently leads to splenic capsular stretch, ischaemia and infarction.

Although wandering spleen may be found incidentally as a mass in the abdomen without causing any complaint, it may cause chronic, subacute or acute abdominal pain secondary to torsion of the splenic pedicle resulting in vascular inflow and outflow thrombosis.

They are often found incidentally at surgery for completely unrelated complaints.


  • Acute torsion of the splenic pedicle with splenic infarction (most common complication)
  • Acute pancreatitis (due to pancreatic tail obstruction)
  • Upper GIT haemorrhage (from gastric fundus varices)


Splenectomy vs Splenopexy.

  • Splenic infarction typically requires splenectomy
  • Spleen preserving strategies (splenopexy) are reserved for healthy & non-infarcted spleens that are of normal size and without signs of hypersplenism.
    • They are highly recommended in paediatric patients to minimise the risk of post-splenectomy septicaemia.

  • Over the next 4 days in hospital our patient is managed conservatively with analgesia.
  • During this time she developed thrombocytosis (PLT > 1100) and was commenced on aspirin.
  • Given the fact she is now functionally asplenic, she was immunised according to a splenectomy program and was also commenced on roxithromycin 150mg daily (for prophylaxis, given penicillin allergy).
  • She received strict instructions on urgent medical review with onset of fever.

  1. Magowska, A. (2013). Wandering spleen: a medical enigma, its natural history and rationalization. World Journal of Surgery, 37(3), 545–550. doi:10.1007/s00268-012-1880-x
  2. Alimoglu, O., Sahin, M., & Akdag, M. (2004). Torsion of a wandering spleen presenting with acute abdomen: a case report. Acta Chirurgica Belgica, 104(2), 221–223.
  3. Anyfantakis, D., et al. (2013). Acute torsion of a wandering spleen in a post-partum female: A case report. International journal of surgery case reports, 4(8), 675–677. doi:10.1016/j.ijscr.2013.05.002

Mind the gap #2…

the case.

a 43 year old male presents to your ED with a three day history of severe epigastric pain and recurrent vomiting. He has now become increasingly breathless and is complaining of severe retrosternal chest pain.

On examination, he is appears unwell and is obviously diaphoretic. He is tachycardic (pulse 130, sinus) with a blood pressure of 148/80. He has no cardiac murmurs or pericardial rub & his chest is surprisingly clear to auscultation despite his respiratory rate of 36 per minute (SaO2 100%, room air). His temperature is normal.

The distinct fruity odour of ketones wafts through the room.

PMHx significant only for moderate, daily alcohol intake.

This is his initial venous blood gas…


BSL 7.2 mmol/L, Ketones “Hi” !!

MTG2 Electrolytes

  • Mild alkalaemia + features consistent with a metabolic acidosis.
    • pH 7.48, HCO3 17, BE -6. pCO2 23.
  • Expected CO2.
    • [HCO3 x 1.5] +8  (±2) – Winter’s formula
    • [17.6 x 1.5] +8
    • 34.4 (±2)
    • Lower than expected pCO2 consistent with additional respiratory alkalosis
  • Alternatively; expected HCO3 (for pCO2 of 23) in acute respiratory alkalosis
    • 24 – [(40 – 23)/10] (x2)
    • 24 – (1.7)x2
    • 20.6
    • This supports the presence of a concomitant metabolic acidosis (w/ actual HCO3 of 17)
  • Anion gap.
    • Na – [Cl + HCO3]
    • 136 – [85 + 15]
    • 36 – ie. markedly elevated – HAGMA.
  • Delta ratio.
    • [AG – 12 / 24 – HCO3]
    • [ 36-12 / 24 – 15 ]
    • 24 / 9
    • 2.67 ~ HAGMA + superimposed Metabolic alkalosis or Respiratory acidosis.
  • Additional findings;
    • Mild hypokalaemia
    • Moderate hypochloraemia
    • Obstructive LFT picture [ALP 354, GGT 846, Bili 60]
      ?Cholangitis ?Cholecystitis ??other
    • Moderate hypomagnesaemia + hypophosphataemia

Interpretation – a triple acid-base disturbance.

  1. High anion-gap metabolic acidosis; likely 2* to starvation or alcoholic ketoacidosis
  2. Hypokalaemic, hypochloraemic metabolic alkalosis; 2* to excessive vomiting [cause to be identified, possible biliary obstruction/cholangitis]
  3. Respiratory alkalosis; ?2* to pain/anxiety

Before getting too deeply entrenched in this topic, attached are basic notes on blood-gas analysis including anion gap & other secondary calculations.


This is used in the presence of a high-anion gap metabolic acidosis [HAGMA] to determine if it is truly a ‘pure’ HAGMA or if there is a coexistence of a normal-anion gap metabolic acidosis [NAGMA] or metabolic alkalosis.

Basic principles & assumptions.

  • If one molecule of acid (HA) is added to extra-cellular fluid & dissociates, the one H+ released will react with one molecule of HCO3 (to produce CO2 + H2O).
  • For every unit increase in an unmeasured ion (ie. anion gap increases by 1) there is a decrease in the serum bicarbonate by 1.
  • The delta ratio quantifies the relationship between the changes in anion gap & bicarbonate. For example: if all acids were to be buffered by bicarbonate, then the increase in anion gap should equal the decrease in bicarbonateThe ratio between these two (known as the DELTA ratio) should be equal to ONE.

The formula & interpretation of results.

Delta Ratio graphic

Delta ratio formula & interpretation of results


Some more specifics.

A low ratio (<0.4):

  • Occurs with a hyperchloraemic (normal-anion gap) acidosis.
  • Chloride (a measured anion) contributes to metabolic acidosis (effectively HCl) creating a low strong-ion difference.
  • The anion gap does not alter, whilst the serum bicarbonate decreases.

A high ratio (>2):

  • Occurs when there is a pre-existing elevated bicarbonate prior to the development of metabolic acidosis.
  • This typically arises from a metabolic alkalosis or compensation for a respiratory acidosis.

Lactic acidosis:

  • Typical delta-ratio in pure lactic acidosis is ~ 1.6 !!
  • Result from intracellular buffering; causing the rise in anion-gap to exceed the fall in bicarbonate.


You should be treating the patient that is in front of you & not just using these numbers in isolation. The chemistry is not perfect & you should have clinical evidence to support your diagnoses.

His ECG demonstrates a sinus tachycardia without features of cardiac ischaemia. His troponin was normal.

Here is his CXR…..


  • Erect CXR demonstrating clear lung fields and normal cardiac silhouette.
  • Retrocardiac air-fluid level adjacent to thoracic spine ?hiatus hernia, however with recurrent vomiting & retrosternal chest pain the differential diagnosis of Boerhaave syndrome needs considering.

With ongoing severe chest pain & an abnormal CXR, the decision is made to proceed to CT to further delineate the pathology.

The chest component of his CT revealed a small hiatus hernia, but no features of Boerhaave syndrome or aortic pathology.

Below is a single axial slice of his arterial-phase contrast CT…


Peri-pancreatic stranding & inflammatory changes consistent with acute pancreatitis


In the short-term our patient was managed with:

  • Analgesia:
    • Titrated intravenous opiates & subsequent Fentanyl PCA
  • IV fluids (kept nil-by-mouth)
    • Maintenance fluids
    • Dextrose infusion (to reverse ketosis)
    • Urinary catheter to guide fluid balance & titration
  • Correction of electrolytes (including potassium, phosphate & magnesium)
  • Thiamine (given history of alcohol intake)

He was admitted to a high-dependency bed under the care of the General Surgeons. His ultrasound failed to show evidence of persistent gallstones or biliary dilatation.

His pancreatitis (?induced by alcohol) was managed conservatively & made a progressive, uneventful recovery of the next 8 days.

  1. Delta ratio - LifeInTheFastLane
  2. Delta ratio – AnaesthesiaMCQ.com

Here are some more case-base examples to work through.

a splitting headache…

the case.

39 year old female presents to your Emergency Department with a four day history of a gradually worsening headache. Whilst she has a past history of migraines, this headache is much more severe and of different character to any migraine she has had previously.

Her husband has bought her in with the concern that she isn’t as ‘alert’ as normal and she ‘isn’t behaving quite right’. The patient continually requests that you “take this splitting headache away!”

She takes regular triptans for her migraines & also has a contraceptive vaginal ring in situ. She has no known allergies.

On examination she is slightly drowsy, has difficulty following commands & is unable to form complete sentences. Her observations are as follows; P 110, BP 140/88, afebrile, SaO2 98% (RA). Cardiorespiratory examination is unremarkable. She has no focal neurological deficits, specifically unremarkable cranial nerves & full limb strength with intact reflexes and sensation. Her gait is not assessed because of her drowsiness.

  • Space occupying lesion [tumour, abscess, other…]
  • Meningoencephalitis [viral vs bacterial vs other…]
  • Subarachnoid haemorrhage or other intracranial haemorrhage [extradural, subdural, intraparenchymal…]
  • Primary headache
  • Carotid or vertebral artery dissection
  • Vasculitis
  • Endocrine or metabolic [less likely…]

Basic laboratory investigations are unremarkable.

– BSL 7.2 mmol/L
– FBC normal
– Na 142 / K 4.3 / Ur 8.4 / Creat 76.
– CRP 21

Given the atypical nature of her headache and her altered mental state, you decide that she needs CNS imaging & send her for a CT…

Non-contrast (axial) CT brain.

Non-contrast (coronal) CT brain.

Non-contrast CT-brain report

Non-contrast CT-brain report

Upon returning from the radiology department, our patient has had an obvious deterioration in her neurological state. She is now obtunded with fluctuating periods of agitation.

Within minutes she has a generalised tonic-clonic seizure !!

Despite several doses of midazolam she continues to have short-lived seizure activity and requires intubation for airway protection and optimisation of ventilation.

With her airway secure, she returns to CT for further advanced imaging…

CT-Venogram (axial).

CT-Venogram (coronal).

CT venogram report

CT venogram report


Thrombosis of the dural sinus and/or cerebral veins (CVT) is an uncommon form of stroke, usually affecting young individuals. Despite advances in the recognition of CVT in recent years, diagnosis and management can be difficult because of the diversity of underlying risk factors and the absence of a uniform treatment approach.

It represents ~0.5-1% of all strokes.

  • 78% occur in patients < 50 years
  • 34% will have an inherited or acquired prothrombotic condition
Cerebral venous anatomy & sites of thrombosis.

Cerebral venous anatomy & sites of thrombosis.


  • Thrombophilias
    • Antithrombin III, Protein C & S deficiencies
    • Antiphospholipid & anticardiolipin antibodies
    • Factor V Leiden
    • Hyperhomocysteinaemia
  • Pregnancy & post-partum period (~6-8 weeks)
  • Oral contraceptive use
  • Malignancy
    • Local affects
    • Hypercoagulable state
    • Medications (eg. Tamoxifen)
  • Infection
    • Para-meningeal infections (ear, sinuses, dental, head & neck)
  • Dehydration
  • Substance abuse especially ecstasy
  • Haematologic
    • Nephrotic syndrome, polycythaemia, thrombocytosis, Fe-deficiency
  • Mechanical
    • Head trauma
    • Neurosurgery
    • Lumbar puncture
  • Systemic diseases
    • SLE
    • Thyroid disease
    • Inflammatory bowel disease
    • Sarcoidosis


Two major categories of clinical findings resulting from;

  1. Increased intracranial pressure (2* to impaired venous drainage)
  2. Focal brain injury from venous ischaemia/infarction or haemorrhage.

Patients typically present with a combination of these features.

  1. Headache is the most common symptom in CVT (~90%).
    • Typically diffuse and progresses in severity over days to weeks
    • Can be sudden & severe (“thunderclap”) or migraine-like.
    • Isolated headache (without neurology or papilloedema) occurs in ~25% of cases.
  2. Altered consciousness
  3. Altered vision
    • 6th nerve palsy
    • Cavernous sinus involvement
  4. Nausea & vomiting
  5. Seizures (focal or generalised, ~40% of cases)

Clinical features are often dependent upon the location of the thrombus (see table below).

Sinus thrombosis location+symptoms



  • Routinely: FBC, biochemistry & baseline coagulation profile
  • Screening for potential prothrombotic conditions may have a role (but won’t help you acutely…)

Lumbar puncture:

  • There are no specific CSF abnormalities in CVT.
  • Opening pressure is elevated in >80% of cases.
  • Elevated cell count & protein is also often seen.


  • A normal D-dimer may be considered to help identify patients with low probability for CVT.
  • However, a normal D-dimer should not preclude further evaluation in patients with high-suspicion for CVT.
  • Evidence limited to small prospective data (~400 patients)



  • Non-contrast CT scans are abnormal in only ~30% of cases.
  • The primary abnormality on a non-contrast CTB is hyperdensity of a cortical vein or dural sinus.

Noncontrast CT showing spontaneous hyperdensity of the right transverse sinus – Case courtesy of Dr Andrew Dixon, Radiopaedia.org. From the case Dural sinus thrombosis and venous infarction

  • Thrombosis of the posterior part of the superior sagittal sinus may result in a dense (or filled) delta sign (see below).
Direct visualisation of a clot in the cerebral veins on a non enhanced CT scan is known as the dense clot sign. ** image courtesy of 'The Radiology Assistant' @ http://www.radiologyassistant.nl/

Direct visualisation of a clot in the cerebral veins on a non enhanced CT scan is known as the dense clot sign. ** image courtesy of ‘The Radiology Assistant’ @ http://www.radiologyassistant.nl/

  • An ischaemic lesion that crosses usual arterial boundaries (or within proximity to a venous sinus) is suggestive of sinus thrombosis.
  • Intracerebral haemorrhage occurs in up to 30-40% of patients with CVT. They often have prodromal headache or bilateral parenchymal abnormalities.

CT Venography:

  • This may demonstrate a filling defect within the cerebral veins or sinuses known as the empty delta sign (see below).
Empty Delta Sign - sinus thrombus creates filling defect on contrast-enhanced CT *image courtesy of MediNuggets

Empty Delta Sign – sinus thrombus creates filling defect on contrast-enhanced CT *image courtesy of MediNuggets

  • A rapid & reliable method of diagnosing CVT
  • More useful in subacute & chronic disease states.
  • Equivalent to MR-venography.

MRI + MR-Venography:

  • More sensitive than CT at each stage after thrombosis.
  • Findings are variable depending on the age of the thrombus.
Case courtesy of Dr Ahmed Abd Rabou, Radiopaedia.org. From the case Dural venous sinus thrombosis

Case courtesy of Dr Ahmed Abd Rabou, Radiopaedia.org. From the case Dural venous sinus thrombosis

CT vs MRI in the Diagnosis of CVT - adapted from Saposnik et al (2011).

CT vs MRI in the Diagnosis of CVT – adapted from Saposnik et al (2011).


(1) Admit to a Stroke Unit.

(2) Anticoagulation.

  • Aim: prevent thrombus extension, facilitate recanalisation & prevent DVT/PE.
  • Initially: 
    • Unfractionated heparin vs Low-molecular weight heparin
    • No data to support one over the other for Mx of CVT.
  • Longer term:
    • Vitamin-K antagonists
    • Aiming for INR 2.0 – 3.0 for 3-6 months in most cases.
  • For advanced interventions – see below.

(3) Seek + Treat Precipitating Causes.

  • This includes bacterial infection (mastoiditis, meningitis etc) with management focusing on antibiotic therapy & surgical drainage of purulent collections.
  • If hormonal therapy if thought to be the culprit; remove the source if able.
  • Thrombophilia screening.

(4) Detect + Correct Complications.

  • Raised intracranial pressure + Hydrocephalus:
    • Consider this with increasing visual symptoms (or deteriorating visual acuity)
    • Management may include medical therapy (eg. acetazolamide), lumbar puncture, optic nerve decompression or shunts.
    • Decompressive craniectomy may be required in the setting of neurological deterioration due to severe mass effect or intracranial haemorrhage refractory to medical therapy.
  • Seizures:
    • Occur in up to 37% of adults (& ~50% of children) with CVT.
    • Anti-epileptic drugs are recommended following a single seizure (without parenchymal lesions).

(5) Advanced Interventions.

  • Fibrinolytic therapy.
    • 9-13% of patients w/ CVT have poor outcomes despite anticoagulation.
    • Recanalisation rates may be higher with thrombolysis, however this is reserved for cases of ongoing deterioration despite anticoagulation (or with increasing ICPs).
  • Direct catheter thrombolysis.
    • One small systematic review (169 patients) showed possible benefit of localised thrombolysis in severe CVT.
    • Carries a higher rate (17%) of intracerebral haemorrhage.
  • Mechanical Thrombectomy/Thrombolysis.
    • Various devices available; evidence is largely anecdotal.
  • Decompressive craniectomy.
    • Reserved for cases of refractory intracranial hypertension.
Algorithm for Management of CVT ** from Saposnik et al. 2011.

Algorithm for Management of CVT ** from Saposnik et al. 2011.

With her CT demonstrating extensive sinus thrombosis, our patient is commenced on a heparin infusion before heading to Intensive Care for ongoing management.

Following extensive thrombophilia screening it is thought that her contraceptive ring was the culprit.

Despite having a rocky inpatient course she is eventually discharged home without neurological deficit with ongoing anticoagulation (warfarin) and levetiracetam for seizure control.

  1. Saposnik, G., et al. Diagnosis and management of cerebral venous thrombosis: a statement for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2011; 42: 1158-1192 doi:10.1161/STR.0b013e31820a8364
  2. Piazza, G. Cerebral venous thrombosis. Circulation, 125(13), 1704–1709. doi:10.1161/CIRCULATIONAHA.111.067835
  3. Dural venous sinus thrombosis – Radiopaedia.org

a covert combination…

the case.

72 year old male presents to your Emergency Department with a 4-5 hour history of palpitations. He appears well and has no associated symptoms.

BP 146/88, SaO2 99% (RA), chest clear.


  • Atrial fibrillation
  • Automatic implantable cardioverter-defibrillator [AICD]
    • Sick sinus syndrome with inducible VT on electrophysiology study
  • Hypertension

Here is his initial 12-lead ECG… ECG#1

Standard rate & calibration.

  •  Rate:
    • 150 bpm.
  • Rhythm.
    • Regular without obvious P waves.
  • Axis.
    • Rightward axis [+129*].
  • Intervals.
    • PR ~ n/a.
    • QRS ~ 160 msec [RBBB morphology]
    • QTc ~ 580 msec.
  • Segments.
    • QRS:T wave discordance
  • Other.
    • Features suggesting VT.
      • Fusion beats seen below (red & blue circles)
      • Monomorphic R-wave in V1.


Broad complex tachycardia with RBBB appearance and features of AV dissociation, highly concerning for ventricular tachycardia.

DDx: Atrial flutter (2:1) + RBBB.

annotated rhythm strip

My approach to any dysrhythmia, fast or slow, is to detect and correct;

  • Ischaemia
  • Electrolytes
  • Medications…

Meanwhile, the patient stays connected to a monitor with defibrillator pads placed for good measure. He is advised to stay nil by mouth, pending the need for sedation. You also arrange for his AICD to be interrogated.

We top up his magnesium and obtain this second ECG….

Broad complex tachycardia at a rate of 136 per minute. RAD. Underlined complex (#5) concerning for AV dissociation.

Broad complex tachycardia at a rate of 136 per minute. RAD. Underlined complex (#5) concerning for AV dissociation.


For more information on VT versus SVT with aberrancy see;

  1. Broad, fast & regular… – the blunt dissection
  2. VT versus SVT with aberrancy via LITFL.com

A-lead demonstrating fibrillation at a rate of 175-375 bpm. V-lead sensing independent ventricular tachycardia at a rate of 136/min.  There is no associated between the atrial & ventricular rhythms.

A-lead demonstrating fibrillation at a rate of 175-375 bpm. V-lead sensing independent ventricular tachycardia at a rate of 136/min. There is no association between the atrial & ventricular rhythms.

Double Tachycardia

ie. ventricular tachycardia with co-existing atrial fibrillation !!

Double tachycardia is a relatively uncommon type of tachycardia. It is classically defined as the simultaneous occurrence of organised atrial and ventricular tachycardias, or junctional and ventricular tachycardias.

Reported causes include;

  • Digitalis toxicity
  • Left ventricular dysfunction
  • Exercise
  • Catecholamine abuse

They can be difficult to diagnose and often require electrophysiology studies for further assessment. Interestingly, the presence of dual-lead ICDs now allow for this non-invasively.

Atrial Fibrillation with AICDs.

Atrial fibrillation is a very common dysrhythmia in patients requiring an AICD.

  • ~20% have AF at time of implantation
  • >50% of patients develop AF during the lifespan of their device.

In the setting of an AICD, AF can result in inappropriate ventricular shocks, ventricular arrhythmia induction & thromboembolism (after ventricular shocks in the presence of unknown AF).

Dual chamber rate-responsive pacing may prevent AF by improving haemodynamics, optimising ventricular filling and preventing retrograde atrial conduction. New overdrive pacing algorithms have been introduced to add incremental anti-arrhythmic benefits to physiological pacing. The aim is that consistent atrial pacing acts to suppress atrial fibrillation.

The PR Logic dual-chamber detection algorithm is widely used in dual-chamber Medtronic ICDs. It discriminates SVTs from ventricular tachycardias using hierarchal rules & timing of atrial and ventricular events.

Double Tachycardia Rules

annotated interrogation

An amiodarone bolus was administered and an infusion commenced following the AICD interrogation. Interestingly, his AICD was programmed to intervene on VT only at a rate exceeding 170 beats per minute.

Approximately 45 minutes into his infusion, our patient dropped his blood pressure into the 70’s with associated clamminess and distress. He received some ketamine sedation and was cardioverted to sinus rhythm.

He was discharged home two days later.

  1. Washizuka, T., Niwano, S., Tsuchida, K., & Aizawa, Y. (1999). AV reentrant and idiopathic ventricular double tachycardias: complicated interactions between two tachycardias. Heart, 81(3), 318–320.
  2. Santini, M., & Ricci, R. (2001). Atrial fibrillation coexisting with ventricular tachycardia: a challenge for dual chamber defibrillators. Heart, 86(3), 253–254.
  3. Weng, K.-P., Chiou, C.-W., Kung, M.-H., Lin, C.-C., & Hsieh, K.-S. (2005). Radiofrequency catheter ablation of coexistent idiopathic left ventricular tachycardia and atrioventricular nodal reentrant tachycardia. Journal of the Chinese Medical Association : JCMA, 68(10), 479–483. doi:10.1016/S1726-4901(09)70078-4
  4. Chowdhry, I. H., Hariman, R. J., Gomes, J. A., & El-Sherif, N. (1983). Transient digitoxic double tachycardia. Chest, 83(4), 686–687.
  5. Brown, M. L., Christensen, J. L., & Gillberg, J. M. (2002). Improved discrimination of VT from SVT in dual-chamber ICDs by combined analysis of dual-chamber intervals and ventricular electrogram morphology, 117–120.
  6. Jason’s Blog: ECG Challenge of the Week for Feb. 24th – March 3rd – another example of a double tachycardia case !!