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?
Show Answer
The correct answer is: E. Dilated cardiomyopathy with dynamic secondary MR
Although a "mitral honk" has been described in the past, this is the first time in the literature that this impressive murmur has been demonstrated on a Doppler echocardiographic recording, as in Video 1.
Differential Diagnosis
A "mitral honk" murmur has no specific correlating pathology but has been described in several conditions.1
Mitral valve prolapse/ballooning can produce mid systolic click followed by a late systolic crescendo or plateau honk. Unlike our patient's murmur, the murmur of prolapse typically increases with inhalation, standing, or Valsalva. These maneuvers decrease the diameter of the LV, increasing the prolapse of the mitral leaflet and thus increasing the regurgitation.
Mitral honk has been described in the setting of an anomalous fibrous chord, which can create a murmur in patients with a dilated ventricle.2 In this instance, maneuvers and situations that create further LV dilatation will pull the chord taut to resonate as a guitar string, thus causing the murmur.
Tricuspid valve prolapse and regurgitation in the setting of pulmonary hypertension could correlate with many changes in murmur with exam maneuvers. It would lessen with greater filling of the right ventricle (inhalation, raising a leg, or moving from standing to lying down) because it would stretch the basal right ventricle, lessen prolapse and regurgitation, and increase with reduced venous return (e.g., expiration or moving from sitting to standing) as lesser filling of the right ventricle lends to a smaller annular diameter with greater leaflet prolapse and regurgitation.
Present Case Findings
Careful transthoracic echocardiography was performed with the physical maneuvers and postures described in Table 1. No anomalous fibrous chord was identified to explain the murmur; however, distinct changes in MR were observed.
Table 1: Proposed Hemodynamic Effects of Exam Maneuvers
Maneuver
LV Preload
LV Afterload
Intrathoracic Pressure
LV & Mitral Annulus Diameter
Murmur
Inspiration
↓
↓
↑
↓
Exhalation
↑
↑
↓
↑
Handgrip
↑
↑
↓
Sit→Stand
↓
↑↑*
↑
↓
Sit→Supine
↑
↑
↓
*Red designates atypical response postulated in this patient.
Findings that were both concordant and discordant with mitral valve prolapase were observed. As expected for a prolapsing mitral valve, increases in the LV diameter that accompanies increased LV preload or afterload decreased the murmur (sitting to lying down and hand grip); see Table 1. Classically, in mitral valve prolapse we expect inspiration to decrease LV preload, lessen the LV basal and mitral annulus diameter, and exacerbate the prolapse-dependent regurgitation. The opposite was seen in our patient. Video 2 demonstrates an increase in MR with inspiration. The decrease in murmur that occurred when our patient stood up was just as unexpected.
Video 2: MR on Four Chamber With Color Doppler and Deep Breathing, Supine
Moderate MR with centrally located, central and posteriorly directed regurgitant jet. With inspiration the regurgitant jet appears to increase in density on color Doppler interrogation and diminish during exhalation. ECG shown as green tracing at top of screen. Spirometry is shown as green tracing on bottom.
We postulate that in this patient with decompensated heart failure, the action of standing up is accompanied by an adrenergic surge leading to vasoconstriction increasing afterload enough to increase the LV and mitral annular diameter, which decreases the regurgitation and murmur. This combination of discordant physical manuever findings in this patient is due to a particular geometry (left ventricluar stretch) assumed by the dysfunctional and dilated LV whose hemodynamics is precariously balanced and is exquisitely sensitive to changes in intravascular volume. A summary of the hemodynamic changes and changes in murmur are described in Table 1.
Further empirical evidence that supports our hypothesis includes high fidelity pericardial pressure tracings needed for transmural pressure measurement and hemodynamic recording during drills of standing, sitting, and supine postures. Without clear clinical indication, these invasive studies could not be justified at the time.Three-dimensional imaging may more definitively show the changes in LV dimension and regurgitant volume suggested, but that was not available during the patient's presentation.
In conclusion, we propose that the "honking" MR in our patient is likely caused by a combination of dynamic coaptation of the mitral valve leaflets in the setting of dilated cardiomyopathy, leading to a situation in which regurgitation is exquisitely influenced by the dynamic volume shifts associated with different postures and physical maneuvers. This is not a common scenario but points to an interesting phenomenon in this patient.
References
Constant J. Bedside Cardiology. Boston: Little, Brown; 1976.
Roberts WC. Anomalous left ventricular band. An unemphasized cause of a precordial musical murmur. Am J Cardiol 1969;23:735-8.
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