Sick sinus syndrome as a late complication after ventricular septal defect surgery

Abstract

Ventricular septal defect is a common congenital heart disease for which patch closure technique using cardiopulmonary bypass has been applied for a few decades, resulting in a low incidence of perioperative complications. We report a 26-year-old woman with bradycardia of 25–30 beats per minute, which was considered to be a late-onset complication of surgical closure of an isolated ventricular septal defect performed 21 years earlier. She has been stable for more than 9 months without an implanted pacemaker, although her heart rate was always around 40 beats per minute in scheduled follow-up visits.

<Learning objective: We experienced a 26-year-old woman with bradycardia of 25–30 beats per minute, which was considered to be a late-onset complication of surgical closure of an isolated ventricular septal defect performed 21 years earlier. Our case highlights the importance of close follow-up for patients who underwent successful surgical closure of a ventricular septal defect and have shown nonsignificant bradycardia, even though they have no symptoms.>

Introduction

Ventricular septal defect is a common congenital heart disease [1] for which patch closure technique using cardiopulmonary bypass has been applied for a few decades, resulting in a low incidence of perioperative complications [2]. We report a 26-year-old woman who was diagnosed as having sick sinus syndrome, which was considered to be a late complication of surgical closure of an isolated ventricular septal defect performed 21 years earlier.

Case report

A 26-year-old woman was admitted to our hospital because of leg edema, weight gain, and bradycardia. She had been well until about a week before admission, when bilateral leg edema developed and her body weight increased by 2.5 kg over 5 days. She saw her physician and was found to have a low pulse rate, approximately 20–30 beats per minute, without dizziness or lightheadedness. She was transferred to the emergency department of our hospital.

The patient had a previous history of surgical closure of a ventricular septal defect at the age of 5 years without any complications. She had been followed up at another hospital until she was 22 years old, and her clinical course after the surgery had reportedly been stable except for a heart rate of 50 beats per minute at the age of 20 years and 42 beats per minute at the age of 22 on standard 12-lead electrocardiogram, without any symptoms. No sign of bradycardia was found before the age of 20 years, although Holter monitoring was not performed. The remainder of the medical history was unremarkable. She was a nutritionist; she was physically active but not an athlete. She had no known allergies and had not taken any medication including supplements. She drank alcohol in moderation, and had never smoked or used illicit drugs. No family history of heart disease including pacemaker implantation was reported.

On examination, the patient was alert. Her blood pressure was 111/56 mm Hg, pulse was 26 beats per minute, and oxygen saturation was 98% while she was breathing ambient air. The jugular veins were distended without Kussmaul's sign; a grade 3/6 holosystolic murmur was audible at the apex, accompanied by Rivero-Carvallo sign, without the third or fourth sounds; the respiratory sound was clear throughout both lung fields; the abdomen was soft without organomegaly or masses; and mild pretibial edema was present on both sides.

An electrocardiogram showed a heart rate of 25–30 beats per minute with a wandering pacemaker, accompanied by poor progression R waves in V1–V3 (Fig. 1). The results of a chest radiograph were normal with a cardiothoracic ratio of 49%. The blood levels of aspartate aminotransferase and alanine aminotransferase were 97 IU/l and 126 IU/l (reference ranges for both, <30 IU/l). The creatine kinase level was 891 IU/l (reference range, <175 IU/l for women), but troponin T and heart-type fatty acid-binding protein were negative. The blood level of N-terminal pro-brain natriuretic peptide was slightly elevated to 98 pg/ml (reference range, ≤55 pg/ml). The complete blood count and blood levels of electrolytes, glucose, lactate dehydrogenase, amylase, and albumin were normal, as were tests of renal function and thyroid function. Echocardiography showed a left ventricular ejection fraction of 60% with trivial mitral regurgitation and moderate tricuspid regurgitation; right ventricular end-diastolic dimension was 44 mm without right ventricular hypertrophy. The remaining echocardiographic findings were normal.

Fig. 1.

A 12-lead electrocardiogram (A), which was obtained at the interval shown by the marked area in continuous monitoring (B), shows that the heart rate fluctuated between 25 and 30 beats per minute, with a wandering pacemaker.

The heart rate transiently increased up to 50 beats per minute after intravenous administration of atropine sulfate at 0.5–1.0 mg, but the effect did not last for more than 10 min. Fortunately, without temporary pacemaker placement, leg edema gradually decreased and finally disappeared after 2-day rest with a low-salt diet, although the patient's heart rate had been almost under 40 beats per minute throughout the day. The blood levels of aspartate aminotransferase, alanine aminotransferase, and creatine kinase were also normalized. Electrophysiological study showed that corrected sinus node recovery time was extended to 2350 ms, which was still prolonged (1960 ms) after intravenous administration of atropine sulfate, with a sinoatrial conduction time of 250 ms, features consistent with sick sinus syndrome. The heart rate increased up to 131 beats per minute (i.e., 68% of the maximum age-predicted heart rate) with a blood pressure of 147/54 mmHg at the fourth stage of Bruce protocol during treadmill testing; electrocardiography showed sinus rhythm with premature atrial contractions, without a sign of sinoatrial block. A head-up tilt without pharmacological provocation was negative; heart rate increased from 42 beats per minute in the supine position to 55 beats per minute during tilting at 70°. The patient was finally diagnosed as having heart failure due to bradycardia. After discharge without an implanted pacemaker or any medication, in line with her and her family's wishes, she has been stable for more than 9 months, although her heart rate was always around 40 beats per minute in scheduled follow-up visits.

Discussion

Ventricular septal defects have been reported to be the most common congenital heart disease [1], accounting for up to around 5% in echocardiographic studies on consecutive newborn infants [3] or randomly selected neonates [4]. Approximately 85–90% of these defects in neonates seem to close spontaneously within a year [3], [5], [6]. Surgical closure of ventricular septal defects has been established for patients with a persistent ventricular septal defect, with low operative mortality and postoperative morbidity [7], leading to almost normal quality of life compared with that of age-matched normal children [8]. As an alternative option, transcatheter techniques for closure of ventricular septal defects have been developed over the past decade [2]. As a result, most adult patients who underwent successful surgical closure of ventricular septal defects in childhood have been discharged from routine follow-up [9], [10], as in our case.

Roos-Hesselink et al. [10] conducted a follow-up study for 95 consecutive patients who had successfully undergone surgical closure of isolated ventricular septal defects at an average age of 4 years (range, 0–13 years). During a median follow-up of 26 years (range, 22–34 years) after surgery, 4 patients (4%) with pulmonary hypertension and right ventricular hypertrophy died suddenly and 6 patients (6%) underwent re-operation due to right ventricular outflow obstruction, residual ventricular septal defect, or discrete subaortic stenosis. Furthermore, 4 patients (4%) underwent additional cardiac surgery: aortic coarctation in 2 patients, persisting arterial duct in 1 patient, and aortic valve replacement after endocarditis in 1. In total, 7 patients (7%) underwent pacemaker implantation: 2 for surgical atrioventricular block shortly after operation and 1 for endocarditis late after surgical closure. Notably, the remaining 4 patients underwent this procedure for sick sinus syndrome more than 15 years after surgery.

The late occurrence of sick sinus syndrome necessitating pacemaker implantation in these 4 patients suggests that sick sinus syndrome in our case could be associated with the surgical closure of a ventricular septal defect performed 21 years earlier. Although the precise mechanism linking surgical closure of an isolated ventricular septal defect and the late occurrence of sick sinus syndrome is unknown, cannulation of the right atrium for cardiopulmonary bypass has been proposed as a possible cause [10], [11]. Other operative incidents might be associated with the late onset of bradycardia, but no detailed information on the surgical procedure for the ventricular septal defect was obtained in our case. Heart rate in our case has slowly decreased over the years, suggesting that practitioners may need to follow up closely patients who underwent successful surgical closure of a ventricular septal defect and have shown nonsignificant bradycardia, for example, 50–60 beats per minute, even though they have neither symptoms nor echocardiographic abnormalities.

Conflict of interest

None of the authors have any conflicts of interest that should be declared.