Critical Care Medicine-Neurologic Disorders>>>>>Acute Coronary Syndrome
Question 4#

A 65-year-old female with hypertension and hyperlipidemia develops substernal chest pressure with dyspnea. Physical exam is notable for the following:

• Blood pressure: 126/62 mm Hg
• pulse: 76 beats per minute
• oxygen saturation of 97% on 4 L nasal cannula General: Sitting up with increased work of breathing
• Heart: Regular rate and rhythm
• A III/VI holosystolic murmur is heard at the cardiac apex, which is nondisplaced on chest palpation
• Lung: Posterior diffuse crackles
• Abdomen: Soft, nontender, and nondistended
• Extremities: Warm, without edema

12-lead electrocardiogram reveals the following:

What is the most likely mechanism of this patient’s dyspnea?

A. Pulmonary embolism
B. Mitral regurgitation
C. LV systolic dysfunction
D. Tamponade

Correct Answer is B

Comment:

Correct Answer: B

The patient presents with a clinical syndrome suggestive of an acute coronary syndrome (ACS). The 12-lead electrocardiogram demonstrates most notably ST segment depressions in the right precordial leads (V1-V3) with prominent R-waves. These findings could suggest a posterior myocardial infarction versus anterior subendocardial ischemia. The presence of prominent R-waves is suspicious for posterior pathologic Qwaves and makes the ST segment depressions more suggestive of infarction. Posterior leads, placed alongside the inferior border of the left scapula (at the same horizontal level as V6), could also be obtained to confirm suspicion of a transmural infarct. Portable echocardiography can be considered to clarify the diagnosis of ST elevation myocardial infarction (STEMI). Early recognition and revascularization are key to managing a posterior STEMI.

The mitral valve has two papillary muscles. The anterolateral papillary muscle receives dual blood supply from the left anterior descending artery and the left circumflex. The posteromedial papillary muscle is supplied only by the posterior descending artery which in most patients branches off the right coronary artery. In posterior myocardial infarctions, attention should be paid to the increased risk of papillary muscle ischemia leading to acute mitral regurgitation. Clinical exam may reveal a holosystolic murmur at the left sternal border with pulmonary edema that corroborates the diagnosis. A murmur, however, may not be heard in up to 50% of cases.

References:

1. Antman EM, Anbe DT, Armstrong PW, et al. ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to revise the 1999 guidelines for the management of patients with acute myocardial infarction). Circulation. 2004;110(9):e82-e292.
2. Casas RE, Marriott HJ, Glancy DL. Value of leads V7-V9 in diagnosing posterior wall acute myocardial infarction and other causes of tall R waves in V1-V2. Am J Cardiol. 1997;80(4):508-509.