Successful Transvenous Implantation of a Permanent Pacemaker in a Patient with Situs Inversus with Dextrocardia Supported by Preceding Three-dimensional Computed Tomography

Abstract

We herein report a 76-year-old woman with situs inversus and dextrocardia who underwent pacemaker implantation for sick sinus syndrome. Situs inversus with dextrocardia, which is frequently associated with cardiovascular malformation, is a rare congenital malformation wherein the thoracic and abdominal viscera are inverted compared with their normal positions. This renders the implantation of cardiac devices an arduous task. We therefore decided to gather preoperative anatomical information on patients with situs inversus and dextrocardia. We used three-dimensional computed tomography to collect preoperative information in order to facilitate the safe implantation of cardiac devices.

Introduction

Dextrocardia is a rare congenital anomaly with an incidence rate of 1 in 12,000 live births (1); the incidence of cardiac abnormalities in these patients is 2-5% (2). Limited reports have described the implantation of a permanent pacemaker for sick sinus syndrome in patients with situs inversus (3). Complex extracardiac and intracardiac anatomies constitute technical challenges for transvenous permanent pacemaker implantation. The most common cardiac abnormalities include anomalous pulmonary veins, transposition complexes, ventricular septal defects, and atrioventricular discordance.

We herein report a patient with situs inversus and dextrocardia who was admitted to our hospital with sick sinus syndrome.

Case Report

A 76-year-old woman was admitted to the hospital with heart failure and shortness of breath on exertion that had persisted for 1 month. Her medical history indicated situs inversus with dextrocardia and coronary artery bypass surgery 10 years prior to presentation.

A physical examination revealed a holosystolic murmur (3/6 on the Levine grading scale) on the right sternal border without any other clinical manifestations of heart failure. Her blood pressure was 118/56 mmHg, and oxygen saturation (SpO₂) was 96% on room air. An electrocardiogram (ECG) at admission revealed a heart rate of 80 beats/min (bpm); P-wave, which was negative in lead I and positive in lead aVR; Q waves in leads I and aVL; and progressively decreasing R-wave amplitude from leads V1 to V6, suggesting dextrocardia (Fig. 1). Transthoracic echocardiography (TTE) in the right lateral recumbent position revealed a reduced systolic function of the left ventricle (left ventricular ejection fraction, 54%; left ventricular end-diastolic volume, 117 mL; left ventricular end-systolic volume, 54 mL). The mitral inflow velocity during early diastole (E) and late diastole (A) ratios were ＞2, indicating diastolic dysfunction, and the pulmonary artery systolic pressure estimated from the tricuspid regurgitation pressure gradient was 46 mmHg. No significant valve regurgitation was observed. The cause of mild heart failure was tachycardia-induced cardiomyopathy.

Figure 1.

A 12-lead ECG from a 76-year-old woman with dextrocardia and situs inversus. A: An ECG demonstrating normal sinus rhythm, right axis deviation, complete right bundle branch block, and Q wave in leads I, aVL, and progressively decreasing R-wave amplitude from leads V1 to V6. B: An ECG from the same patient, obtained after right-sided repositioning of the precordial leads (V1-V6). An ECG demonstrating normal sinus rhythm with increasing R-wave progression in the precordial leads. ECG: electrocardiogram

During hospitalization, repeated tachycardia due to paroxysmal atrial fibrillation and sinus arrest were observed on an ECG monitor. Pauses lasting ＞3 s, which led to the patient experiencing loss of consciousness and nausea, were observed frequently (Fig. 2). The 24-h Holter ECG revealed an average heart rate of 124 bpm, a maximum heart rate associated with paroxysmal atrial fibrillation of 163 bpm, and a minimum heart rate of 32 bpm, accompanied by a pause of 8.3 s. The patient was diagnosed with sick sinus syndrome (Rubenstein classification, type III). Thus, permanent pacemaker implantation was scheduled.

Figure 2.

The monitored ECG during hospitalization shows a long pause after termination of atrial tachycardia. ECG: electrocardiogram

To assess the vascular anatomy and minimize radiation exposure during pacemaker implantation, three-dimensional computed tomography (3D-CT) was performed to characterize the anatomic configuration. We observed a right aortic arch with a mirror-image branching pattern, liver on the left side, and stomach and spleen on the right side of the abdomen, suggesting situs inversus. A 3D-CT scan presenting the venous system in blue and the left ventricle in yellow is shown in Fig. 3A and B. Visualization of the subclavian vessels confirmed that there were no significant abnormalities in vessel movement. Therefore, the insertion site could be approached from the left side. However, because it was difficult to determine the presence of venous stenosis at the site where the left subclavian vein intersected the left clavicle, an intraoperative angiogram was scheduled for final determination. As no cardiac malformations were observed, we assumed that an atrial lead could be placed in the right auricle and therefore opted for dual-chamber pacing.

Figure 3.

3D-CT on the left shows the status of the patient post-coronary artery bypass surgery (A). 3D-CT on the right shows the cardiac vascular structure: superior vena cava (light blue), right atrium (green), right ventricle (blue), left atrium (purple), and left ventricle (yellow) (B). 3D-CT: three- dimensional computed tomography, LA: left atrium, LV: left ventricle, RA: right atrium, RV: right ventricle, SVC: superior vena cava

Bilateral subclavian venography along with right ventriculography was performed during the preoperative evaluation. Venous lines were placed bilaterally, and venous access was achieved through the left subclavian vein. Furthermore, as no stenosis of the left subclavian vein was detected, an approach from the left side was initiated as planned. The right subclavian vein was punctured using a vein puncture technique under local anesthesia; subsequently, pacing leads were implanted first in the right ventricle and then in the right atrium under fluoroscopic guidance. A tined lead was used for the right atrium, and a screw-in lead was used for the right ventricle. The right ventricle lead was positioned in the mid-septum and the right atrial lead in the right auricle. The actual side targeted for the right ventricle lead was advanced through the tricuspid valve, and then the tip was positioned directly against the interventricular septum with a manually shaped stylet and screwed on the interventricular septum. The leads were positioned while monitoring the fluoroscopic images; images taken at the 50° left anterior oblique (LAO) (Fig. 4A) and 30° right anterior oblique (RAO) positions (Fig. 4B) verified the position of the leads. The device was programmed as a dual-chamber pacemaker at 60-130 bpm with good sensitivity and threshold.

Figure 4.

Fluoroscopic views in the 50° LAO (A) and 30° RAO positions (B). One with correct lead placement in the septum and the other with the lead placed in the right atrium. LAO: left anterior oblique, RAO: right anterior oblique

Post-permanent pacemaker implantation findings revealed a reduced cardiothoracic ratio on chest radiography, decreased pleural effusion, and improvement in the rate of heart failure (Fig. 5). The patient was discharged on foot without any complications, and a follow-up outpatient visit one month later revealed no clinical or functional problems with the device.

Figure 5.

Chest X-ray findings before (A) and after pacemaker implantation (B). Lung congestion and pleural effusion disappeared, and the cardiothoracic ratio normalized after pacemaker implantation (B).

Discussion

Complicated malformations associated with the inversion of internal organs in situ are often observed in cardiovascular and gastrointestinal systems. In normal subjects, the incidence of cardiac malformations in the cardiovascular system is 0.32-0.8%, whereas that in visceral inversion is 8-10%, an approximately 10-fold higher incidence (1). Situs is defined as the development of the heart on the right side, wherein the heart is predominantly in the right thorax.

There are three types of situs: situs solitus (normal), situs inversus (mirror image of normal), and situs ambiguity or isomerism (visceroatrial isomerism) (4). Isomerism is further classified as right (two morphologically right atria), left (two morphologically left atria), or unspecified. The incidence rates of these three types are similar (1). Situs solitus is a normal visceroatrial arrangement located in the right inferior vena cava and right superior vena cava, connecting to the right atrium on the right side of the heart, with the liver on the right side, and the stomach on the left side. Situs inversus is a mirror image of a normal visceroatrial arrangement located in the left inferior vena cava and left superior vena cava connecting to the right atrium on the left side of the heart. In the present case, the liver was on the left side and the stomach was on the right side; however, the anteroposterior relationships of various parts of the heart were normal. Thus, the underlying mechanism of situs inversus with dextrocardia mirrors that of the heart along with other visceral organs (including the liver and stomach) rather than heart malrotation alone.

In general surgery, situs inversus with dextrocardia complicates pacemaker implantation. This is because the individual anatomy of the patient may preclude device implantation. Careful preplanning is necessary before pacemaker implantation. 3D-CT is often performed before pulmonary vein isolation to provide detailed anatomical information regarding the pulmonary veins, left atrium, and surrounding structures (4). Abnormal anatomy of the right atrium and ventricle, such as congenital heart disease, may affect pacemaker lead placement. Therefore, by performing preoperative 3D-CT, we can fully understand the positional relationship and blood vessel distribution in the organs before surgery. Pacemaker leads were placed on the septal side of the right ventricle to regulate the electrical activity of the heart effectively. The position of the heart cavity is reversed in the reverse position of situs inversus with dextrocardia. Therefore, to function optimally, the leads must be inserted into the corresponding reverse chamber. We must fully understand the 3D anatomy and adapt our approach accordingly in such cases.

In addition, the venous system carries pacemaker leads from the subclavian vein to the right atrium and ventricle. Anatomical variations in the venous system, such as abnormal venous connections or the absence of certain veins, can complicate lead placement (5). The presence of complex congenital anomalies in patients with situs inversus and dextrocardia is associated with systemic veins (6). If an abnormality occurs during operation of the venous system, the position of the device can be changed. If sufficient information cannot be obtained in advance, fluoroscopic images are used to check the course of the blood vessels. However, this increases the surgical and radiation exposure times as well as the amount of contrast agent used.

Some operators flip the fluoroscopic image from left to right to recreate the standard left ventricular orientation (7,8); however, we successfully implanted the device in a patient while in the standard view without using inverted images.

A preimplantation evaluation with 3D-CT can detect congenital anatomical abnormalities and provide useful information for surgical planning, resulting in an uneventful operation. Preoperative 3D-CT allows for the visualization of the anatomy of the heart and blood vessels, thus enabling proper planning of the percutaneous approach.

Conclusions

Permanent pacemaker implantation can be safely and effectively performed in patients with dextrocardia and situs inversus using 3D-CT guidance to facilitate lead positioning. A preimplantation assessment with cardiac 3D-CT can help detect congenital anatomical anomalies and provide helpful information for operative planning.

The authors state that they have no Conflict of Interest (COI).