MEDizzy - A 75-year-old man presents to your emergency department

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Disorders of the Cardiovascular System

A 75-year-old man presents to your emergency department appearing quite ill. His family says he has not had his normal energy for the last 6 months, and they noted he was confused and lethargic for the last day or two. As you take a history from the family, you palpate the patient’s radial pulse and notice a regular beat-to-beat variability of pulse amplitude, although his rhythm is regular. Indeed, as you later take his blood pressure, you note that only every other phase I (systolic) Korotkof sound is audible as the cuff pressure is slowly lowered and that this is independent of the respiratory cycle. Based on this, you suspect this patient has which of the following?

ExplanationThis patient has evidence of pulsus alternans. Pulsus alternans is defined by beat-to-beat variability of pulse amplitude. It is present only when every other phase I Korotkof sound is audible as the cuff pressure is lowered slowly, typically in a patient with a regular heart rhythm and independent of the respiratory cycle. Pulsus alternans is seen in patients with severe left ventricular systolic dysfunction and is thought to be due to cyclic changes in intracellular calcium and action potential duration. When pulsus alternans are associated with electrocardiographic T-wave alternans, the risk for an arrhythmic event appears to be increased. Cardiac tamponade or large pericardial effusions can be associated with electrical alternans (a regular variability in the QRS voltage or vector) or pulsus paradoxus, a difference between the systolic pressure at which the Korotkof sounds are first heard (during expiration) and the systolic pressure at which the Korotkof sounds are heard with each heartbeat, independent of the respiratory phase. This is an exaggerated consequence of interventricular dependence. Atrial fibrillation would result in beat-to-beat variability of the pulse amplitude but also an irregularly irregular rhythm.