More Evidence that Inspiratory Threshold Device Improves CPR

More evidence that inspiratory threshold device improves CPR (but only when CPR is done right!): 

Resuscitation online



Abstract

Objectives
To determine if the quality of CPR had a significant interaction with the primary study intervention in the NIH PRIMED trial.
Design
The public access database from the NIH PRIMED trial was accessed to determine if there was an interaction between quality of CPR performance, intervention, and outcome (survival to hospital discharge with modified Rankin Score (mRS) ≤3).
Setting
Multi-centered prehospital care systems across North America.
Patients
Of 8719 adult patients enrolled, CPR quality was electronically recorded for compression rate, depth, and fraction in 6199 (71.1%), 3750 (43.0%) and 6204 (71.2%) subjects, respectively. “Acceptable” quality CPR was defined prospectively as simultaneous provision of a compression rate of 100/min (±20%), depth of 5 cm (±20%) and fraction of >50%. Significant interaction was considered as p < 0.05.
Intervention
Standard CPR with an activated versus sham (inactivated) ITD.
Measurements and main results
Overall, 848 and 827 patients, respectively, in the active and sham-ITD groups had “acceptable” CPR quality performed (n = 1675). There was a significant interaction between the active and sham-ITD and compression rate, depth and fraction as well as their combinations. The strongest interaction was seen with all three parameters combined (unadjusted and adjusted interaction p-value, <0 .001="" 34="" acceptable="" active-itd="" all="" an="" compared="" cpr="" discharge="" for="" hospital="" i="" increased="" mrs="" of="" performed="" presenting="" quality="" respectively="" rhythms="" sham="" survival="" to="" use="" versus="" was="" when="" with="">p
= 0.006). The opposite was true for patients that did not receive “acceptable” quality of CPR. In those patients, use of an active – ITD led to significantly worse survival to hospital discharge with mRS ≤3 compared to sham (34/1012 [3.4%] versus 62/1061 [5.8%], p = 0.007).
Conclusions

There was a statistically significant interaction between the quality of CPR provided, intervention, and survival to hospital discharge with mRS ≤3 in the NIH PRIMED trial. Quality of CPR delivered can be an underestimated effect modifier in CPR clinical trials.

Cardiac Arrest and ST Elevation: You Should Learn to Recognize This!

The following case was incredibly interesting for other reasons, but in order to maintain confidentiality and also to allow for a subsequent case report by the physicians caring for the patient, I limit the discussion to the ECG findings and their etiology.

A man was resuscitated from an Asystolic Cardiac Arrest with Epi, bicarb, and chest compressions.  He was in shock.  

Here was the initial 12-lead:
This is nearly pathognomonic of at least one condition.  What is it?












There is sinus rhythm with a prolonged QRS, right precordial ST elevation, and very peaked T-waves in V4-V6.   This is hyperkalemia until proven otherwise.

It is possible that the ST elevation is due to STEMI, but unlikely.

Hyperkalemia often produces a Brugada-like right precordial PseudoSTEMI pattern.

The pH was 6.65, with a K of 7.5 mEq/L.

Here are 7 other examples of PseudoSTEMI due to HyperK:
1. http://hqmeded-ecg.blogspot.com/2013/06/a-tragic-case-related-to-last-post.html
2. http://hqmeded-ecg.blogspot.com/2013/11/you-must-recognize-this-pattern-even-if.html
3. http://hqmeded-ecg.blogspot.com/2013/06/hyperkalemia-and-st-segment-elevation.html
4. http://hqmeded-ecg.blogspot.com/2013/06/this-ecg-is-pathognomonic-of-life.html
5. (there are 3 in this post): http://hqmeded-ecg.blogspot.com/2013/02/right-bundle-branch-block-with-st.html


There is remarkably little literature on ECG findings in severe acidosis.
Here is a case in which one patient had 2 cardiac arrests on separate dates, both due to cocaine use, and both with severe acidosis and a bizarre Brugada-like ECG. 



He was given Calcium, bicarbonate, and Insulin


This ECG was recorded 30 minutes after the first:
Same findings, but less pronounced, and slower rate

The pH at this point was 6.80, with a K of 6.2 mEq/L.  More Calcium and Bicarb were given.



At 1 hour, with a pH of 6.95 and K of 7.2 (difficult to control), another ECG was recorded:
Similar

Cardiac Arrest and ST Elevation: You Should Learn to Recognize This!

The following case was incredibly interesting for other reasons, but in order to maintain confidentiality and also to allow for a subsequent case report by the physicians caring for the patient, I limit the discussion to the ECG findings and their etiology.

A man was resuscitated from an Asystolic Cardiac Arrest with Epi, bicarb, and chest compressions.  He was in shock.  

Here was the initial 12-lead:
This is nearly pathognomonic of at least one condition.  What is it?












There is sinus rhythm with a prolonged QRS, right precordial ST elevation, and very peaked T-waves in V4-V6.   This is hyperkalemia until proven otherwise.

It is possible that the ST elevation is due to STEMI, but unlikely.

Hyperkalemia often produces a Brugada-like right precordial PseudoSTEMI pattern.

The pH was 6.65, with a K of 7.5 mEq/L.

Here are 7 other examples of PseudoSTEMI due to HyperK:
1. http://hqmeded-ecg.blogspot.com/2013/06/a-tragic-case-related-to-last-post.html
2. http://hqmeded-ecg.blogspot.com/2013/11/you-must-recognize-this-pattern-even-if.html
3. http://hqmeded-ecg.blogspot.com/2013/06/hyperkalemia-and-st-segment-elevation.html
4. http://hqmeded-ecg.blogspot.com/2013/06/this-ecg-is-pathognomonic-of-life.html
5. (there are 3 in this post): http://hqmeded-ecg.blogspot.com/2013/02/right-bundle-branch-block-with-st.html


There is remarkably little literature on ECG findings in severe acidosis.
Here is a case in which one patient had 2 cardiac arrests on separate dates, both due to cocaine use, and both with severe acidosis and a bizarre Brugada-like ECG. 



He was given Calcium, bicarbonate, and Insulin


This ECG was recorded 30 minutes after the first:
Same findings, but less pronounced, and slower rate

The pH at this point was 6.80, with a K of 6.2 mEq/L.  More Calcium and Bicarb were given.



At 1 hour, with a pH of 6.95 and K of 7.2 (difficult to control), another ECG was recorded:
Similar

Early Repolarization, Anterior MI, or Other?

A 30 something presented with atypical chest pain.

Here is the ECG:
--There is huge ST elevation in V2 and V3, approximately 5 mm.
--There is some ST elevation in aVL with some minimal reciprocal ST depression in III
--There is a small q-wave in V4.
--There are also large S-waves in I and II, and a large R-wave in V1, suggesting right ventricular hypertrophy


It is risky to apply the early repol vs. LAD occlusion formula when there are other indications that this may be MI, such as 1) Q-wave in V4 and 2) STE in aVL with STD in III.  However, when I saw this (I did not take care of the patient), I thought this "looked" like early repol, and I did apply the formula:

STE 60 V3 = 5 mm
QTc = 411 ms
R-wave amplitude in V4 = 25 mm

Formula value = 22.079.  This is very low.  Less than 22 is about 97% sensitive for LAD occlusion.

This is very low.  Serial ECGs were recorded and they remained the same.  The patient ruled out for MI and all ECGs were stable.

Unfortunately, no echo was done to assess for RV hypertrophy.

Learning Points

1.  Early repolarization can have Scary ST elevation
2.  Pretest Probability is Critical.  Here, the low pretest probability was an important factor in this decision: in a young patient with atypical pain, scary ST elevation is much less likely to be due to ischemia.





Four Great Instructional SMACC Videos from Hennepin

These great procedural videos on online at SMACC.  All done at Hennepin County Medical Center's Emergency Department by my incredible colleagues.

All are embedded below.

3 were Winners of the SMACC instructional video contest  (Winners in September, April, and May)

Minnesota Tube by Drs. Jacoby, Helland, Simpson, and Joing (WINNER)
ILMA by Drs. Rowland-Fisher, Joing, Prekker, and Reardon (WINNER)
Williams Airway by Drs. Kornas, Rowland-Fisher, Joing, and Reardon 
Nasopharyngoscopy by Drs. Paetow, Rowland-Fisher, and Reardon (WINNER)


September Winner

Minnesota Tube from Social Media and Critical Care on Vimeo.


May Winner

Nasopharyngoscopy from Social Media and Critical Care on Vimeo.

Emergency Physicians Must Make the Tough Decisions

This recent case, which occurred within the past year, was sent to me by an unnamed 2nd year EM resident.  She says she is a believer in all things FOAM!

As this case could have been managed better, she will remain anonymous.  But rather than being critical of the management, just try to learn from it.


Case presentation:
A middle-aged woman with a history of vascular disease presented to a community Emergency Department after an episode of syncope. She complained of 24 hours of severe chest pain radiating to her back, and epigastric abdominal pain. Initial vital signs were BP 128/85, HR 122, RR 22 and O2 saturation was 98% on room air. Physical exam was significant for diaphoresis and agitation, tachycardia without murmurs, epigastric abdominal tenderness without rebound or guarding, and equal peripheral pulses.

An ECG was recorded:
This ECG is notable for narrow-complex sinus tachycardia, ST segment elevation with Qr-waves (deep Q, small r-wave) in V1-V2 and T wave inversions in V1-V4. There are no reciprocal ST segment depressions.

Is this an acute MI?
The presence of such well developed Q-waves in the anterior leads suggests that this is not an acute STEMI, but rather a subacute anterior MI.

What is your next step?


























A bedside ultrasound was performed:


This is a subxyphoid cardiac view demonstrating moderate pericardial fluid.  The LV appears to have reasonable function, but is rather small, suggesting poor filling.  I do not have an image of the IVC.  The aortic root was not imaged.

Is this pericardial tamponade?

Upon close inspection of the right ventricle, you can see that there is no collapse during diastole. The RV appears to be both filling and squeezing well, which argues against pericardial tamponade.  

On the other hand, the patient has tachycardia and probable poor LV filling, so a fluid challenge would be appropriate.

Comment: What is the pericardial fluid?

In the setting of subacute MI, one must entertain the idea of myocardial free wall rupture.  Aortic dissection with leakage into the pericardial sac is certainly a possibility, but this would require 2 unusual events:
1) a delayed presentation (dissection with pericardial blood is usually so acute that the patient would present immediately after onset of symptoms).
2) Focal Anterior STEMI.  Though dissections can dissect down the left main, they are
        a) less common that the RCA
        b) more deadly (if there is Left main occlusion)
                i) when not deadly (incomplete occlusion), they present with diffuse ST depression, not anterior ST elevation (this ECG is consistent with LAD occlusion).

Patient course

The resident wanted to do pericardiocentesis, but was not allowed by her faculty.  Labs were significant for initial mild troponin elevation (2.8 ng/mL), consistent with subacute MI. 

CT scan was performed due to suspicion for aortic dissection and was negative. Unfortunately the patient became hemodynamically unstable shortly after returning from the CT scanner.  Fluids were started. The hemoglobin returned very low and so blood was transfused.  Mental status declined and she was intubated, then went into PEA arrest (comment: "pulseless" electrical activity means that pulses cannot be felt, not that there is no perfusion and certainly not that there is no cardiac activity).  Chest compressions were begun and Cardiac surgery was called.  She did regain pulses at times and would have spontaneous movements, but would lose pulses again.

Comments:

1) Chest compressions are probably not helpful.  They can improve venous return to the chest if done in conjunction with an ITD, but the problem is that the LV cannot fill, NOT that it cannot pump.  The resident recognized the futility of chest compressions.

2) In the setting of tamponade, positive pressure ventilation may be fatal.  It decreases venous return.  Poor cardiac filling is the problem.  Positive pressure ventilation makes it worse.  Ventilation will not help a patient who has no circulation.  Intubation should be a last resort.  The intrathoracic pressure regulator (CirQLator, see references far at bottom) is an FDA-approved device that sucks air out of the endotracheal tube starting at end-expiration, and this may be the solution for patients who have poor venous return but need intubation.  Unfortunately, this device is not yet commercially available even though it is FDA approved.

Case continued:

At the time of the arrival of the chest surgeon much later, the patient no longer had reactive pupils and was undergoing chest compressions.

The diagnosis of myocardial rupture was considered.  The surgeon performed a thoracotomy in the ED, which revealed blood and large clots within the pericardial sac and a small anterior wall perforation. Attempts to suture the defect failed due to friability of the surrounding tissue. Open cardiac massage and aggressive resuscitation with blood products failed to achieve ROSC and the patient was pronounced dead approximately four hours after initial presentation.

Final diagnosis: myocardial rupture

The resident presented this as an "M and M" at her institution and "the sentiment was that thoracotomy in the ED in this setting would be extreme and even frowned upon," and that the diagnosis of free wall rupture is perceived to be uniformly rapidly fatal.




Comment:

Early recognition and thoracotomy, best done in the OR, or even earlier pericardiocentesis with subsequent rapid OR thoracotomy, could have been life saving in this patient who was relatively young.

This is a clear case in which one or both of pericardiocentesis or ED thoracotomy would be indicated and possibly life saving.  Emergency physicians must take the lead.  Myocardial rupture must be highest on the differential.  Treatment should be simultaneous with consultation with a cardiac surgeon, and should be fluids first, pericardiocentesis if fluids do not stabilize, and thoracotomy if the patient is in a downward spiral (or if pericardiocentesis is inhibited by pericardial thrombus).

This is a good case for demonstrating that emergency medicine must make the decisions and take the lead.  One cannot wait for cardiologists or cardiac surgeons, although of course the surgeon has to agree to take the patient to the OR.  The best way to get the surgeon to agree to take the patient to the OR is if the emergency physician successfully resuscitates FIRST; then there is no choice!

Myocardial rupture:
Mechanical complications of complete transmural myocardial infarction (untreated persistent STEMI, or treated STEMI with No-Reflow phenomenon) include ventricular free wall rupture (VFWR), inter-ventricular septum rupture, papillary muscle rupture and atrial rupture. Among these diagnoses, VFWR is the most common, occurring in 1.7% of 849 patients in the Multicenter Investigation of the Limitation of Infarct Size, published in 1989.


Ventricular free-wall rupture (VFWR, commonly referred to as cardiac rupture) typically presents either as sudden cardiac death or, less commonly, with chest pain, hypotension, syncope, cardiogenic shock or obstructive shock due to pericardial tamponade. Myocardial rupture typically occurs between 1-5 days after infarct, but has been documented weeks after AMI. Rupture can also occur early.  The “rupture” may actually be more like a slow leak developing over hours to days. Diagnosis can be made by ultrasound, which may demonstrate pericardial fluid or clot with or without tamponade and may even provide visualization of the defect in the myocardial wall. Like other mechanical complications, treatment is immediate surgical repair.

Risk factors for myocardial rupture include first MI, single vessel disease, lack of collateral flow, transmural infarct (STEMI), female gender, advanced age, anterior MI, and delayed or no reperfusion. Patients treated with thrombolytics have higher rates of rupture than those who undergo percutaneous intervention, especially when thrombolytics are given 12- 24 hours after symptoms.

ECG in Myocardial Rupture

Myocardial rupture is preceded by post-infarct regional pericarditis (PIRP) in the majority of cases.  See this paper on myocardial rupture and this paper on postinfarction regional pericarditis, both by Oliva et al. (and both full text links).  

Full-thickness infarct causes localized inflammation of the epicardium (PIRP).  So PIRP is a sign of full thickness infarct, which is the harbinger of myocardial rupture. Persistently positive T-waves or premature (upright) reversal of previous T-wave inversions after STEMI is suspicious for PIRP and the patient may be at risk for rupture. (See a case of PIRP and interventricular septum rupture here: http://hqmeded-ecg.blogspot.com/2014/07/subacute-anteroseptal-stemi-with.html).  

This case of rupture is unusual in that T-waves remained inverted.  

Temporizing measures may include pericardiocentesis and volume loading (for tamponade). Overall mortality is high, but not inevitable; there is also high intraoperative mortality.  Survival is higher when there is witnessed event, early medical intervention, and receipt of care at a facility with cardiac surgery.

In a large study, twenty-five (76%) of the 33 patients with subacute ventricular rapture survived the surgical procedure and 16 (48.5%) were long-term survivors.

At our institution (Hennepin County Medical Center), Dr. David Plummer reported in 1994 on 6 cases of STEMI that were diagnosed as myocardial rupture by bedside ultrasound in the ED.  2 of the 6 survived surgery.  This is not a uniformly fatal condition!

Aortic dissection was appropriately considered in the differential, but the patient should only undergo CT if stable.  This would be a great time to use ultrasound to look at the aorta.  ED Transthoracic ultrasound is pretty sensitive and specific.  


Transesophageal echo will be an important tool for the ED in the future.

Other mechanical complications of Acute STEMI

Interventricular septum rupture causes left-to-right shunting and symptoms include progressive dyspnea, heart failure, palpable thrill and a new holosystolic murmur (2). It occurs in an estimated 1-2% of all AMIs (2,3).  (I think this is overstated as well.)  Diagnosis is made by Doppler ultrasound, and treatment is surgical correction of the defect.  See this case.

Papillary muscle rupture is a result of posterior MI (inferoposterior or posterolateral or isolated posterior), and occurs in 1-3% of patients with AMI within 3-5 days. This mechanical defect leads to sudden onset dyspnea and acute pulmonary edema, and may also present with a new systolic murmur characteristic of mitral regurgitation.  However, the defective valve area is often so large that there is little turbulence and often no murmur.  Diagnosis is made by suspicion and then ultrasound with Doppler.  The ED treatment is intubation with mechanical ventilation and paralysis to decrease myocardial oxygen demand, nitroprusside to decrease afterload, intra-aortic balloon pump, and surgical repair.  See these 2 cases.


Learning points:

1. Include myocardial rupture in the differential for anyone with subacute MI AND persistent ST elevation, especially with tachycardia or hypotension.   Confirm with bedside ultrasound.  If pericardial fluid is found, aortic dissection should be pursued in a very acute situation. 

2. Findings consistent with PIRP on ECG, new murmur, pericardial fluid, hemodynamic instability, or acute pulmonary edema should make one suspicious of a mechanical compication to acute MI.

3. Perform bedside echo early if suspicious for these diagnoses and consult surgery immediately if echo shows pericardial fluid or clot.

4. Not all patients with mechanical complications of MI die suddenly; early recognition, stabilization and surgical repair can be life saving.  

5. Positive pressure ventilation is detrimental in tamponade.


References (CirQLator references are at the bottom):
1.   Plummer et al. Emergency Department Two-Dimensional Echocardiography in the Diagnosis of Nontraumatic Cardiac Rupture. Annals of Emergency Medicine. 1994 June 23;6: 1333-42.
2.     Sinikka P-S et al.  Ventiruclar septal and free wall rupture complicating acute myocardial infarction: Experience in the Multicenter Investigation of Limitation of Infarct Size.  Am Ht J 117(4):809-818; April 1989.
3.     Lopez-Sendon J et al.  Diagnosis of subacute ventricular wall rupture after acute myocardial infarction: Sensitivity and specificity of clinical, hemodynamic and echocardiographic criteria.  JACC 19(6):1145-1153; 1992.
4.     Sahibzada et al. Ventricular Free Wall Rupture. Journal of Ayub Medical College, Abbottabad. 2009 21;2.
5.     Moreno et al. Primary angioplasty reduces the risk of left ventricular free wall rupture compared to thrombolysis in acute MI. Journal of the American College of Cardiology. 2002 Feb 20;39 (4):598-603
6.     Smith et al. Myocardial Rupture and Postinfarction Pericarditis. In: The ECG in Acute MI. 2002 Lippincot Williams & Wilkins.
7.     Predictive factors of cardiac rupture in patients with ST-elevation myocardial infarction. Journal of Zhejiang University Science B. 2014 Dec 15;12:1048-54
8.     Wehrens et al. Cardiac rupture complicating myocardial infarction. American Journal of Cardiology. 2004 95:285-92
9.     Large transmural STEMI with myocardial “rupture” of the ventricular septum.  From: Dr. Smith’s ECG Blog.  http://hqmeded-ecg.blogspot.com/2014/07/subacute-anteroseptal-stemi-with.html
10. Haddadin et al. Surgical treatment of postinfarction left ventricular free wall rupture. Journal of Cardiac Surgery. 2009 Nov 24;6: 624–31. 
11.   Oliva PB, Hammill SC, Edwards WD. Cardiac rupture, a clinically predictable complication of acute myocardial infarction: report of 70 cases with clinicopathologic correlations. J Am Coll Cardiol 1993;22:720-6.
12.   Oliva PB, Hammill SC, Edwards WD. Electrocardiographic diagnosis of postinfarction regional pericarditis: ancillary observations regarding the effect of reperfusion on the rapidity and amplitude of T wave inversion after acute myocardial infarction. Circulation 1993;88:896-904.
13.     Hollander and Diercks. Acute coronary syndromes: Acute myocardial infarction and unstable angina. In: Tintinalli et al. Tintinalli’s Emergency Medicine 6th Ed. New York: McGraw-Hill.

14.     Ashfaq et al. Mechanical complications following acute myocardial infarction. Journal of Pakistan Medical Association. 2012 Aug 62;8:861-5.


CirQLator (intrathoracic pressure regulator)

This is a study I published in which we studied the use of an Impedance Threshold Device on awake, non-intubated, hypotensive patients:
http://www.sciencedirect.com/science/article/pii/S0736467910003859