ECG of the Week – 21st May 2018 – Interpretation

This ECG is from a 42yr old female who presented complaining of palpitations following an elective procedure in general anaesthetic earlier that day.


Click to enlarge


Rate:

  • 66 bpm mean ventricular rate
Rhythm:
  • Two distinct rhythms
  • Complexes #1-3 and #11
    • Sinus
    • Rate 60 bpm
    • Normal QRS width
  • Complexes #4-10
    • Non-sinus
    • Rate 63 bpm
    • QRS Prolonged
    • AV dissociation
      • Atrial activity buried in QRS
Axis:
  • Unable to determine due to rhythmm change
Intervals for sinus complexes:
  • PR - Normal (~160ms)
  • QRS - Normal (80ms)
  • QT - 400ms
Intervals for non-sinus rhythm:
  • QRS - Prolonged (120ms)
Additional:
  • Non-specific conduction delay not typical BBB
  • No evidence of fusion or capture during non-sinus rhythm
Interpretation:
  • Episode of accelerated idioventricular rhythm (AIVR)
What happened ?

The are a number of potential causes of AIVR in patients including:
  • Ischaemia
  • Post-reperfusion
  • Drug toxicity / effect especially digoxin and other anti-arrhythmics
  • Athletic heart
  • Electrolyte abnormalities
  • Structural cardiac disease
  • Myocarditis
AIVR occurs when the rate of the ectopic ventricular pacemaker exceeds that of the sinus node. This patient was observed in the Emergency Department and normal biochemistry and negative biomarkers. The episodes of AIVR resolved and were felt to be secondary to volatile anaesthetic and she was discharged with out-patient cardiac follow-up.

References / Further Reading

Life in the Fast Lane

Textbook
  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.

VA AM Report 5.21.18: Hypoglycemia and adrenal insufficiency

Case summary: Thanks to our favorite R3/intern centaur Daniel Kwon, who presented the case of a 60M with PMH HIV on ARVs who presented with dyspnea due to a viral pneumonia and was found to have adrenal insufficiency due to ritonavir potentiation of inhaled nasal steroids!

Top pearls:

  1. In evaluating a patient with hypoglycemia, ensure you confirm Whipple’s triad: 1)  hypoglycemia is not a lab error (repeat FSBG and ensure it correlates with serum glucose on a Chem panel), 2) the patient has symptoms of hypoglycemia while hypoglycemic, 3) the patient’s symptoms are relieved with reversal. Finally, if you’re entertaining the diagnosis of insulinoma, ensure you draw the labs for work-up (e.g. C peptide) while the patient is hypoglycemic.
  2. VA hospitalist and medical educator extraordinaire Denise Connor wrote up a fantastic case in JAMA IM reviewing causes of false FSBG readings, which range from shock and PVD to Waldenstrom’s macroglobinemia.
  3. Ritonavir and other CYP450 inhibitors can potentiate the action of steroids that are not typically systemically active (topical, inhaled, nasal) and lead to adrenal insufficiency and iatrogenic Cushing’s syndrome.
  4. Urine studies in hyponatremia due to adrenal insufficiency mimic SIADH (see mechanism below, and thanks to Renal attending Naomi Anker for the teaching!).

“Pseudohypoglycemia”: When FSBG readings don’t reflect serum [glucose]

  • Type 1: FSBGs accurately reflect glucose levels in the microcirculation, but are considerably lower than the systemic plasma glucose owing to sluggish capillary blood flow.
    • shock
    • peripheral vascular disease
    • cyanotic heart disease
    • acrocyanosis
    • Raynaud phenomenon
    • scleroderma
  • Type 2: in vitro glycolysis in the collection tube
    • leukemia
    • polycythemia
    • Waldenström macroglobulinemia

Here is the fantastic Teachable Moment case on pseudohypoglycemia from Denise Connor et al.: Wang EY, Patrick L, Connor D. Blind Obedience and an Unnecessary Workup for Hypoglycemia: A Teachable Moment. JAMA Intern Med. 2018 Feb 01; 178(2):279-280.

Here is a review of protease inhibitor-mediated potentiation of nasal/inhaled steroids: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3758391/


What causes hyponatremia in adrenal insufficiency?

  • Big picture: low cortisol–> CRH–> ADH–> hyponatremia
  • Urine studies therefore are indistinguishable from SIADH

hyponatremia


We like the Endocrine society breakdown for classifying causes of hypoglycemia: ill/medicated or well

Ill/medicated

  • Drugs (insulin, secretagogues, adulterated illicit drugs, alcohol, lots of prescription meds)
  • Critical illness (hepatic, renal, cardiac failure; sepsis)
  • Hormone deficiency (adrenal insufficiency)

Well

  • Insulinoma
  • Other rare disorders (functional beta cell disorders from other pancreatic tumors or post-gastric bypass, insulin autoimmune hypoglycemia)
  • Accidental or surreptitious insulin/secretagogue ingestion

Autism screening

This month’s Podcast of the Month is from Primary Care Perspectives.

In a 30 minute podcast Kate Wallis (Developmental and Behavioural Paediatrician, Children’s Hospital of Philadelphia) discusses the pros and cons of the M-CHAT when screening for autism in the primary care setting. She also shares some helpful tips for picky eaters.

Is the M-CHAT a useful screening tool for non-pervasive developmental disorders?

If you only line up one podcast this month, make it this one.

Listen to the podcast.

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