UMEM Educational Pearls - Cardiology

Increasing literature over recent years has demonstrated that young women (1) DO have MIs, (2) present more atypically than men, and (3) are more often misdiagnosed than men. Two recent trials have now also confirmed that young women have a higher in-hospital mortality compared to men, even when properly diagnosed. They may be due to lack of aggressive workups or treatment, or perhaps other as-yet unidentified factors.

The takeaway points are simple: be very wary when women (incuding young women) present with any cardiopulmonary complaints or anginal equivalent-type symptoms; and treat them aggressively.

Show References

Here's some numbers to consider regarding typical radiation exposre associated with cardiac imaging tests relative to naturally occurring background radiation exposure:

Test type                                                                                     Relative exposure       
Naturally occurring annual background radiation
   exposure for a person living in the US (~ 3 mSv)                                  1
Coronary artery calcium score                                                                0.5
Cardiac CT angiography                                                                         1-4
Nuclear stress test (single-photon emission CT)                                       3-4
Exercise treadmiil testing (with no imaging)                                             0
Cardiac MRI/echocardiogram                                                                   0

[above estimates are typical, but may vary between individuals and among different centers]

Show References

[Pearl provided by Dr. Semhar Tewelde]

Who are the experts at deciphering ECG's

Authors looked at 240 ECGs which activated the cath  lab activation for STEMI.   They excluded patients with LBBB or paced rhythms.  Retrospective chart reviews were used to determine if there was actually a STEMI. The ECGs were then shown to 7 experienced interventional cardiologists and interpreted for acute STEMI.  

Of 84 subjects, there were 40 patients with a true STEMI and 44 without (13 of whom had NSTEMI)  Recommendations for immediate PCI varied widely, from 33%-75%.  Sensitivities were 53%-83%, specificities 32%-86%, PPV 52%-79%, and NPV 67%-79%. When the cardiologist chose non-ischemic ST elevation, LVH was thought to be the cause in 6% to 31% and old MI/aneurysm in 10% to 26%.

Moral, even cardiologists can be wrong... EM physicians must scrutinize every ECG and challenge ourselves to be the best at interpreting ECG's.

Show References

(from Dr. Semhar Tewelde)

Stress testing is one modality used to screen for CAD. The goal is to identify a fixed obstruction to coronary blood flow (typically plaque > 50%) such as in stable angina. However, in ACS, both USA and AMI, the underlying pathophysiology is plaque rupture (typically  plaque < 50%) and thrombus formation that may not have been significant enough to cause a positive stress test.

The use of a prior negative stress test to determine the disposition of ED chest pain patients is questionable. The history of present illness should dictate patient disposition. In one study 20.7% of patients presenting to the ED with a negative stress test within three years of presentation still had significant CAD defined as a positive cardiac markers, subsequent positive stress test of any type, cardiac catheterization requiring intervention, or death due to medical cardiac arrest within 30 days of ED presentation.

 

Show References

(Pearl provided by Dr. Semhar Tewelde)

Physiological LV hypertrophy in trained athletes is defined by an isolated increase in QRS amplitude, normal axis, normal atrial and ventricular activations patterns, and normal ST-segment T-wave replorization; athletes of African/Caribbean descent have prominent cardiovascular remodeling leading to pronounced voltage criteria for LV hypertrophy and BER

Despite the presence of voltage criteria for LVH, pure QRS voltage criteria for LVH in an asymptomatic athlete without family hx of cardiovascular diseases or SCD, and lack of non-voltage ECG criteria does not warrant systematic evaluation with echocardiography.

In other words, young patients, especially men, especially those of African/Caribbean descent, will be expected to have large voltage QRS complexes and sometimes abnormal repolarization, and this is not necessarily a pathologic finding.

Show References

Pearl provided by Dr. Semhar Tewelde

The Athlete's Heart and ECG Abnormalities
Up to 80% of athletes have common training related ECG changes/abnormalities including: sinus bradycardia, asymptomatic sinus pause, sinus arrhythmia, first degree AV block, incomplete right bundle branch block, benign early repolarization (BER), and isolated QRS voltage criteria for left ventricular (LV) hypertrophy.

Approximately 5% athletes exhibit uncommon training unrelated ECG changes/abnormalities including: T-wave inversions, ST-depression, pathological Q-waves, left axis deviation/left anterior fasicular block, right axis deviation/left posterior fasicular block, right ventricular hypertrophy, complete left or right bundle branch block, long or short QT interval, ventricular pre-excitation/WPW, Brugada pattern, and arrhythmogenic right ventricular dysplasia (ARVD).

Show References

Cardiogenic shock pearls from Dr. Semhar Tewelde:

1. CS is most commonly secondary to a large MI where > 40% of the myocardium is involved; however mechanical, valvular, dysrhythmogenic, and infectious etiologies should also be considered: papillary or chordal dysfunction, free wall or septal defects disease, insuffiency of any valve, myopericarditis, endocarditis, Tako-tsubo, end stage cardiomyopathy, and tamponade.
2. Incidence of 5-10% STEMI and 2.5-5% NSTEMI
3. Mortality ~50%
4. Immediate coronary reperfusion is the best treatment (NNT 8). Medical therapy is a distant second choice in management, with reperfusion and pressors as needed. Early intra-aortic balloon pump use is key.
5. Recent case reports have shown imporved outcomes when induced hypothermia was used in patients refractory to traditional therapy with pressors/inotropes/IABP.

How likely is coronary artery disease to occur in young patients?
An autopsy series in US communities evaluated young patients (avg age 36 years old) who died of "non-natural" causes revealed coronary atherosclerosis in > 80% of the autopsy sample, with 8% having significant obstructive disease.

The bottom line is simple....be wary of discounting the risk of ACS purely based on a patient's age. The HPI is the most important factor in predicting ACS.

Show References

A recent study in JAMA has provided further evidence regarding some key issues in ACS/MI presentations which seem to be commonly taught but often forgotten in actual practice. Here's just a few of the key findings from this study:
1. Generally speaking, women were more likely to present without chest pain than men, and the difference between the sexes was most apparent in the < 45yo groups. Overall, 42% of women presented with painless MIs. [remember from a recent prior cardiology pearl that painless MIs have a higher mortality as well]
2. Women had a higher mortality than men within the same age groups, and the difference between the sexes was most apparent in younger ages.
3. Almost 1/5 of women < 45 yo with MI did not report chest pain. [We've always assumed it's just the older women that present with painless MIs....not true!]

A final point that should be re-stated: young women DO have MIs, they DO often present without pain, and they DO often die. Be wary.

Show References

Quick pearls on cardiogenic shock

Post-MI cardiogenic shock is associated with a mortality of 50-70%. There are only a few interventions that have been demonstrated to improve outcomes: early use of intra-aortic balloon pump, stenting, and G2B3A inhibitors.

It is generally recommended to avoid clopidogrel since so many of these patients will require CABG.

Early use of mechanical ventilation decreases work of breathing and improves oxygenation.

Remember that age alone is not a contraindication to aggressive treatment.
 

Show References

You might think that patients with painless MIs might have a better prognosis than patients with pain. Unfortunately, this is just not true. A recent study (1) supported prior literature indicating that the lack of pain is not a predictor of a more benign course, and in fact patients with painless MIs have a higher in-hospital and 1-year mortality. There are several other factors that may associate lack of pain with worse outcomes (e.g. painless MIs occur more often in older patients), but regardless it's important to remember that (1) many patients with MI will present without pain, and (2) the lack of "typical" symptoms should not be reassuring.

Show References

As many as 1/3 of patients with proven ACS have no chest pain at presentation. Among the more common alternative presentations (anginal equivalents) are dyspnea, diaphoresis, nausea/vomiting, and syncope/near-syncope.

Note also that the absence of pain does not confer a better prognosis. The overall in-hospital mortality rate for patients with painless presentations is 13% vs. 4.3% for patients with chest pain.

Show References

We've noted studies in recent years indicating that cardiac risk factors are ineffective at predicting the likelihood of ACS in patients with acute chest pain (in other words, it's all about the HPI and EKG!). Now there's evidence also that cardiac risk factors are ineffective at predicting in-hospital mortality in patients that rule in for acute MI. [1]  In fact, this study actually demonstrated that in-hospital mortality is inversely related to the number of cardiac risk factors!

The bottom line is simple: cardiac risk factors are useful at predicting long-term risk for development of coronary artery disease, but they are NOT useful at in the acute setting.

Show References

Patients with ACS are often treated early with clopidogrel. However, if the patient with ACS appears to be developing cardiogenic shock, its probably best to withhold the early clopidogrel. The literature indicates that patients with cardiogentic shock benefit most from emergent PCI, and many of these patients will need CABG. Generally it's best to avoid clopidogrel in patients heading for CABG.

The use of clopidogrel in patients with cardiogenic shock can be deferred to the cardiologists in the cath lab once they decide whether the patient will need CABG or not.

Show References

Feeling a bit guilty about over-eating during these holidays? Here's a study that might make you feel just a tad bit better about those extra pounds. (Just a tad.)

Auer and colleagues reviewed coronary angiograms of over 1000 patients and correlated them with body fat percentage. After statistical analysis, they found that body fat was not associated with the presence (or absence) or severity (size of coronary lesions) of atherosclerosis in men or women. Furthermore, the results did not differ based on age.

What's the takeaway point? Simple: go ahead and have that second serving of ham and eat that extra slice of cake!

[disclaimer: This study has not necessarily been reproduced, and is not intended to give free license to gorge after the holidays are done. It is fully expected that starting on January 2 you will immediately forget all of the above and renew your commitment to a healthy lifestyle consisting of a bland diet and P90X or Insanity workouts on a daily basis. But until then, forget the guilt!]

Show References

There are a handful of conditions associated with a rightward axis on the ECG: left posterior fascicular block, ventricular ectopy, lateral MI (old), pulmonary hypertension (acute or chronic), right ventricular hypertrophy, hyperkalemia, misplaced leads, and toxicity of sodium channel blocking drugs, to name a few.

When you notice that the rightward axis is NEW compared to an old ECG, and there's nothing else on the ECG that's obviously diagnostic (e.g. hyperkalemia would also show peaked Ts; ventricular tachycardia would be wide complex and fast, etc.), in emergency medicine you should always think first and foremost of the following three possibilities:
1. acute pulmonary embolus
2. toxicity of a sodium channel blocking drug
3. misplaced leads

Pay attention to axis! Using the above rule can make rightward axis very simple and useful.

AM
 

Show References

Minimizing interruptions in chest compressions during CPR is critically important. As an example of the adverse consequences of interruptions, consider the following finding from Edelson (Resuscitation 2010): for every 10 seconds of hands-off time during cardiac arrest, the patient's chances of successful return of spontaneous circulation decreases by 50% due to reductions in cerebral perfusion.

Next time you are involved in a code, keep this in mind, and do EVERYTHING POSSIBLE to minimize those interruptions in chest compressions.

 

Show References

Right heart endocarditis is much more common in patients that are injection drug users. Fortunately for them, they have a lower mortality than patients with left heart endocarditis because they have a lower rate of developing heart failure. This is a reminder that the most common cause of death from endocarditis is heart failure.

Reasons for acutely elevated troponins
ACS
Acute heart failure
PE
Stroke
Aortic dissection
Tachyarrhythmias
Shock
Sepsis
Perimyocarditis
Endocarditis
Tako-tsubo cardiomyopathy
Cardiac contusion
Strenuous excercise
Sympathomimetic drugs
Chemotherapy

I guess that means that your history, physical, and clinical judgment still supersede the lab test.

Show References

Blood pressure cuffs tend to OVERESTIMATE true blood pressure in obese patients. Even larger cuffs tend to do this as well. While low blood pressures are often reliable in diagnosing shock, be wary of  assuming a "normal" blood pressure (e.g. SBP 100-120s) rules out shock in an obese patient who is sick. A-lines might be necessary to accurately assess the blood pressure.

[adapted from ACEP talk by Dr. Tiffany Osborn]