A Thrilling Precordial "Honk"

A 76-year-old male patient with a history of hypertension, gout, and ischemic cardiomyopathy has severely reduced systolic function and a dilated heart status post biventricular pacemaker defibrillator with multiple admissions for heart failure over the past 2 years. He presented to the emergency department with worsening paroxysmal nocturnal dyspnea and dyspnea on exertion over the last 3 days. He denied other significant complaints on review of systems.

The physical exam was notable for the patient sitting up in bed and breathing comfortably on room air. An electrocardiogram (ECG) demonstrated sinus rhythm with biventricular pacing. He had a palpable thrill in the precordium, no S1, a faint S2, a 6/6 late systolic crescendo murmur that was loudest at the apex with increased intensity with expiration but decreased intensity to 3/6 with inspiration. Changing position from sitting upright to lying down temporarily abolished the murmur for several minutes. Similarly, changing position from lying supine to standing also briefly abolished the murmur. Hand grip diminished the murmur. Over the following 2 days, the patient was diuresed and the murmur became increasingly sensitive to the maneuvers that decreased the intensity.

The transthoracic echocardiogram showed the following:

  • Left ventricular (LV) dilatation
  • Severely reduced global LV systolic function
  • Reduced right ventricular systolic function
  • Small-to-medium pericardial effusion
  • Moderate-to-severe mitral regurgitation (MR) with centrally located, central, and posteriorly directed regurgitant jet
  • Trace aortic regurgitation
  • No aortic stenosis
  • Mild tricuspid regurgitation
  • Trace pulmonic regurgitation

The cardiac catheterization performed on the third day in the hospital showed the following:

  • Mildly elevated LV end-diastolic pressure (15 mm Hg)
  • 50% lesion in mid left anterior descending
  • No aortic stenosis

Further discussion with the patient revealed that he periodically hears his own heart murmur, noting that it varies with posture and respiratory cycle. The same description had been recorded previously in a review of systems on admission 2 years ago, but no significant murmur was documented at that time.

Audio 1: Chest Auscultation at Apex of Heart, Recumbent Position

Faint S2, 6/6 late crescendo systolic murmur loudest at the apex with increased intensity with expiration.

Video 1: Continuous Wave Doppler of Mitral Valve, Supine

Continuous wave Doppler tracing of mitral valve inflow and MR with standard Doppler audio signal recording. There is a typical mid-peaking systolic Doppler signal seen with MR and correlating high-pitched Doppler audio signal. In late systole, a second low-pitched "honk" is heard over the first high-pitched sound. The "honk" correlated with timing of a thrill felt by the sonographer. ECG shown as green tracing at top of screen. Spirometer shown as green tracing on bottom.

What is the cause of this murmur?

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