UMEM Educational Pearls - By Amal Mattu

Which patient has a better blood pressure, the patient with a blood pressure of 110/40 or the patient with a blood pressure of 90/60?

Mean arterial pressure (MAP) is generally considered to be the organ perfusion pressure in an individual. Because MAP requires an inconvenient calculation, we've all been taught...misled perhaps...into focusing on systolic blood pressure (SBP) as a marker of how well-perfused a patient is, and we tend to ignore the diastolic blood pressure (DBP).

It's important to remember, however, that we spend most of our lives in diastole, not systole. As a result, our organs spend more time being perfused during diastole than systole. The MAP takes this into account: MAP = (SBP + DBP + DBP)/3. DBP is more important than SBP!

So which patient is perfusing his vital organs better, the one with a BP of 110/40 or the one with a BP of 90/60? Do the MAP calculation...90/60 is better than 110/40!

Pay more attention to those diastolic BPs!

[Pearls provided by Dr. Semhar Tewelde]

Cocaine...
1. causes systolic and diastolic dysfunction, arrhythmias, and atherosclerosis even in young users with relatively few cardiac risk factors, typically TIMI risk score <1

2. decreases myocardial contractility and ejection fraction by blocking sodium and potassium channels within the myocardium

3. prolongs the PR, QRS, and QT intervals on the ECG

4. users have a higher overall incidence of MI (odds ratio 3.8 to 6.9)

5. -induced chest pain is associated with acute MI in approx. 6% of cases

6. increases the risk of MI by 24-fold in the first hour after use

7. contributes to approx. 1 of every 4 MIs  between 18 and 45 years of age

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For patients presenting to the ED with chest pain,  we've been taught that “classic” or “typical” presentations for ACS (chest pressure with radiation to the left neck/jaw/shoulder/arm, dyspnea, diaphoresis, nausea, vomiting, lightheadedness) are most worrisome. Yet, many of the patients that present with typical symptoms end up having negative workups for ACS. What are the symptoms that truly predict ACS? Three major studies have demonstrated that the best predictors of ACS in patients presenting to the ED with chest pain are (not necessarily ranked in order):
1. chest pain that radiates to the arms, especially if the pain radiates bilaterally or to the right arm
2. chest pain associated with diaphoresis
3. chest pain associated with vomiting
4. chest pain associated with exertion

The description of the chest pain (e.g. "pressure" or "squeezing," etc.), the dyspnea, nausea, lightheadedness, and pain at rest were, surprisingly, not helpful at predicting ACS.

The simple takehome point is the following: always ask your patient with chest pain if the pain radiates, if there was associated diaphoresis, if there was associated vomiting, and if the pain is associated with exertion. If the answers to any of these 4 questions is "yes," think twice before labeling the patient with a non-ACS diagnosis.

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New studies are utilizing mild therapeutic hypothermia as a treatment option in cardiogenic shock. These studies have reported improved circulatory support, an increase in systemic vascular resistance, and reduction in vasopressor use which ultimately may result in lower cardiac oxygen consumption. The preliminary results suggest that mild therapeutic hypothermia could be a therapeutic option in hemodynamically unstable patients independent of current recommendations which support its use in cardiac arrest survivors.

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[pearl provided by Dr. Semhar Tewelde]

Myocarditis is an under-diagnosed cardiac disease resulting from a broad range of infectious, immune, and toxic etiologies

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[pearl provided by Dr. Semhar Tewelde]

Peripartum cardiomyopathy (PPCM) is a relatively rare idiopathic form of heart failure that occurs during the last months of pregnancy or the first months after delivery

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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.

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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]

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[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.

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(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.

 

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(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.

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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).

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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.

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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.

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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.
 

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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.

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The WBC count is normal in up to 45% of elderly patients with bacteremia. The most predictive factors for bacteremia in the elderly are delirium, vomiting, bandemia, and tachypnea.

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