Review Question - QID 218246

This patient who presents with dyspnea on exertion, orthopnea, bibasilar crackles, and an S3 heart sound most likely has heart failure. This condition is associated with elevated brain natriuretic peptide (BNP) levels.

A post-systolic ventricular gallop (also known as an S3 heart sound) occurs just after systole and occurs with the opening of the mitral valve. While an S3 heart sound may be normal in children and athletes, most patients with an S3 are in a volume overloaded state. In these patients, increased volumes of blood move from the left atrium to a compliant left ventricle resulting in a characteristic low-pitched sound as blood fills the chamber. One common cause of S3 gallops is systolic heart failure with decreased left ventricular contractility and increased end systolic volumes. The volume overload in these patients causes increased atrial stretch resulting in increased release of BNP. Of note, some heart failure medications can artificially raise BNP levels but N-terminal pro-BNP is specific for overload conditions. The diagnosis of heart failure can further be supported with echocardiography.

Marcus et al. studied whether the occurrence of an audible S3 or S4 gallop was correlated with objective markers of heart function. They found that the S3 gallop is superior to the S4 gallop in detecting left ventricular dysfunction. They recommend that objective measures such as echocardiogram be used given the low sensitivity and specificity of these heart sounds.

Incorrect Answers:
Answer 2: Elevated D-dimer levels indicate increased levels of thrombolysis and would be seen in patients with a pulmonary embolism. These patients may also present with tachypnea; however, other symptoms include tachycardia, pleuritic chest pain, and increased oxygen requirement. The diagnosis would be confirmed with CT angiography of the chest or a V/Q scan (though this is a less optimal test).

Answer 3: Elevated isoprostaglandin levels indicate increased rates of endovascular oxidative stress and would be seen in patients with hypertension. These patients are often asymptomatic but can also present with headaches or palpitations. Prolonged untreated hypertension can result in arteriolosclerosis and myocardial ischemia.

Answer 4: Elevated procalcitonin levels indicate increased immune cell activity and would be seen in patients with pneumonia. These patients would present with productive cough, fever, night sweats, and malaise. This marker is thought to be associated with bacterial rather than viral infection; however, this may not be supported by current data reliably.

Answer 5: Elevated troponin levels indicated increased levels of cardiac myocyte damage and would be seen in patients with a myocardial infarction. These patients would present with chest pain and possibly ST-changes on an ECG. Troponin levels may also be elevated in other conditions such as sepsis and rhabdomyolysis.

Bullet Summary:
An S3 heart sound is caused by volume overloaded states such as heart failure and is associated with increased levels of brain natriuretic peptide.