A 45-year-old woman participates in a cardiovascular health study. She undergoes continuous 24-hour ECG monitoring with a wearable device. A few instances of the following pattern were found on her ECG:
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Which of the following best represents the relative left ventricular end-diastolic volumes just prior to the heart beats represented by the letters?
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The beat marked by the letter Y in this patient is a premature ventricular contraction (PVC), recognized by a wide QRS complex, opposite-facing T wave, and brief ensuing sinus pause (ie, delayed P wave). PVCs may result from increased ventricular automaticity leading to spontaneous ventricular depolarization. Occasional PVCs are normal and considered benign.
When a PVC occurs, it interrupts diastolic filling of the left ventricle, resulting in decreased end-diastolic volume (EDV) compared to the previous normal beat (beat X > Y). The sinus pause that occurs after a PVC allows for longer-than-normal filling time before the next ventricular contraction (ie, prolonged ventricular diastole), which creates increased EDV at the time of the post-PVC beat (beat Z > X). The greater-than-normal EDV causes a large-stroke volume ventricular ejection, which may be responsible for the palpitations that some patients experience with PVCs.
Educational objective:
A premature ventricular contraction is recognized on ECG by a wide QRS complex, opposite-facing T wave, and brief ensuing sinus pause. Left ventricular filling is less than normal at the time of the PVC. The ensuing sinus pause allows for greater-than-normal filling during the post-PVC beat.