Additional heart sounds during early diastole in a patient with hypertrophic cardiomyopathy and atrioventricular block

Abstract

IntroductionA fourth heart sound (S4) is sometimes difficult to differentiate from a third heart sound (S3) in some conditions, such as tachycardia or arrhythmia, because both S3 and S4 are perceived as a low-pitched sound and can be distinguished mainly based on the timing in the cardiac cycle [1]. We report a case with hypertrophic cardiomyopathy and Wenckebach second-degree atrioventricular block, in which the S4 was initially misdiagnosed as an S3 on auscultation and later confirmed using a phonocardiogram with an apexcardiogram. Case reportA 77-year-old man with nonobstructive hypertrophic cardiomyopathy underwent phonocardiography in Matsushita Memorial Hospital. Wenckebach second-degree atrioventricular block had developed several years earlier, but he had been doing well without any symptoms or cardiovascular events. The patient had dyslipidemia and Dubin-Johnson syndrome. His mother reportedly had left ventricular hypertrophy. Medications included mexiletine hydrochloride, warfarin potassium, diltiazem hydrochloride, rebamipide, and pravastatin sodium.On examination, the blood pressure was 140/70 mmHg and the pulse was irregular, with a rate of 78 beats per minute. First heart sound (S1) and second heart sound (S2) were normal with no murmurs. An S4 was faintly audible at the apex in the left lateral decubitus position. Interestingly, other additional heart sounds during early diastole were alternately heard best at the apex, but also at the right and left sternal borders. A presumed diagnosis of S3 was made. The remainder of the examination was normal. An electrocardiogram showed normal sinus rhythm with a rate of 75 beats per minute, right axis deviation, ST-T changes, and isolated premature ventricular contractions; progressively increased PR intervals, sometimes followed by a dropped QRS, were diagnostic of Wenckebach second-degree atrioventricular block that was unchanged from previous findings.A phonocardiogram with microphones placed at the second right sternal border and the apex in the left lateral decubitus A B S T R A C T A third heart sound (S3) and a fourth heart sound (S4) are similarly perceived as low-pitched sounds and can be difficult to distinguish in some conditions, such as tachycardia or arrhythmia. We report a case with hypertrophic cardiomyopathy and Wenckebach second-degree atrioventricular block, in which the S4 was initially misdiagnosed as an S3 on auscultation and later confirmed using a phonocardiogram with an apexcardiogram. Interestingly, the amplitude of the S4 dynamically and regularly fluctuated in proportion to the interval between the S4 and the preceding ventricular contraction. These findings were associated with transmitral inflow patterns assessed by Doppler echocardiography, highlighting the importance of not only transmitral A but also E waves for the amplitude of S4 in patients with arrhythmias. <Learning objective: A fourth heart sound could be difficult to diagnose and dynamically fluctuate in amplitude in patients with arrhythmias, such as Wenckebach second-...

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