Coronary Revascularization in Adults with Dextrocardia

Abstract

Most reports of coronary artery bypass grafting in adult patients with dextrocardia have focused on the surgeon's position with respect to the operating table. Herein, we describe the cases of 2 patients with dextrocardia who underwent surgery at our own institution, then discuss preoperative evaluation, surgical approaches, and patient outcomes that have been reported in the medical literature. Whereas most patients, including ours, have presented with classic situs inversus totalis and dextrocardia, a few patients have had other associated anomalies or atypical morphologic conditions. Careful imaging, and perhaps cardiac catheterization, is required. Particular attention should be paid to cannulation technique and conduits that can best be used within the altered orientation of the heart. Morbidity rates in these revascularized patients seem comparable with those in coronary artery bypass patients whose coronary anatomy is normal. Anatomic variants in dextrocardia are important from the surgical viewpoint due to the increasing population of patients with repaired congenital heart disease who reach adulthood, and in whom other cardiac defects and abnormalities of cardiac position are common.

Most patients who present for coronary artery bypass grafting (CABG) have a normally positioned cardiac mass (levocardia), an apex on the left, and a typical atrial arrangement (atrial situs solitus). However, a small number of adults who present for CABG have dextrocardia in which the main cardiac mass is to the right of the midline and the cardiac apex faces toward the right. Many of these patients have a mirror-image arrangement of the atrial appendages (situs inversus [SI]) and abdominal viscera (SI totalis). In some cases of dextrocardia, both atrial appendages are of either right or left morphology (atrial isomerism). All patients with dextrocardia present unique surgical challenges with respect to the cannulation technique for cardiopulmonary bypass (CPB), the choice of graft conduits, graft configuration, and where the surgeon stands when operating on the patient. Preoperative evaluation should focus on the influence of anatomic variants—an aspect of surgical strategy that is not necessarily a primary focus when patients with typical coronary anatomy present for CABG. Herein, we describe the cases of 2 of our own patients with dextrocardia who underwent CABG, and we review other reports in the medical literature, emphasizing the surgical implications of anatomic variants in dextrocardia.

Case Reports

We performed CABG successfully in 2 patients with dextrocardia. Both were men (ages, 63 and 57 yr) with SI totalis and 3-vessel coronary artery disease, Canadian Cardiovascular Society (CCS) class II angina symptoms, and good left ventricular (LV) function (ejection fraction, >0.50). Preoperatively, both patients underwent coronary angiography, 12-lead electrocardiography (ECG), chest radiography, transthoracic echocardiography (TTE), and abdominal ultrasonography. Besides SI totalis, neither patient had other evident cardiac or extracardiac anomalies. Surgery was performed using CPB, with mild hypothermia (35 °C) and intermittent antegrade cold-blood cardioplegic solution. A right-handed surgeon performed both operations while standing on the left side of the operating table. In each patient, the right internal thoracic artery (RITA) was mobilized as a pedicle and anastomosed to the left anterior descending coronary artery (LAD), and long saphenous vein grafts (SVGs) were anastomosed to the posterior descending and 1st obtuse marginal vessels. Both patients were weaned from CPB with no inotropic support and were discharged from the hospital on their 5th postoperative days. One patient developed atrial fibrillation on postoperative day 3 and underwent successful chemical cardioversion after being given intravenous amiodarone. Both patients were in stable condition and asymptomatic as of the 18- and 30-month follow-up examination, respectively.

Coronary Artery Bypass Grafting in Dextrocardia: Literature Review

We found 28 English-language reports of CABG in adult patients with dextrocardia (Table I).^1–28 The reports, from various centers, described 32 patients. Their mean age was 59.7 years, and 23 were men (72%). Like our 2 patients, most had dextrocardia with SI totalis and no other cardiac or extracardiac anomalies. One patient had pseudodextrocardia related to heart displacement that was associated with eventration of the diaphragm.²⁶ Two patients had atrial situs solitus with isolated dextroposition of the heart^7,15; in 1, this condition was related to a left diaphragmatic hernia.¹⁵ Of 2 patients with atypical cardiac structures, 1 had situs ambiguus and polysplenia,¹⁸ and the other had situs solitus and congenitally corrected transposition of the great arteries (ccTGA).²¹ In regard to comorbidities, 8 patients had presented acutely with unstable angina, postinfarction angina, or heart failure.3,5,7,13–15,24,27 Four patients underwent emergent CABG,6,14,26,27 and 1 of them had an intra-aortic balloon pump inserted before surgery.²⁷ One patient had undergone prior renal transplantation,¹⁸ and 1 had previously experienced pulmonary embolism.¹⁰

TABLE I. Characteristics of the Studies

Of the 32 patients, 20 underwent CABG with the use of CPB (ONCAB) and 11 without (OPCAB); 1 report⁴ did not specify this (Table II). In 1 OPCAB procedure, conversion to ONCAB was required intraoperatively.¹³ Eight ONCAB patients were given antegrade cold cardioplegic solution (either crystalloid or blood),1,2,5,9,10,23 and 1 was given warm-blood cardioplegic solution.¹⁹ Two reports described the use of both antegrade and retrograde cardioplegia.^17,18 Only 10 of the 20 ONCAB reports specified patients' CPB times (range, 38–130 min) and cross-clamp times (range, 34–69 min). In regard to the chosen conduits, 6 patients received only venous grafts,^1–3,15 7 received only arterial grafts,4,5,12,16,19,20,27 and 19 received both types (Table II). Among anastomoses to the LAD, 5 patients received venous conduits, 19 received the RITA, and 2 received the left ITA (LITA). In 1 patient, the LITA was harvested, but it was too small and provided poor flow, so a venous graft was used as a substitute.¹⁵

TABLE II. Intraoperative Data on the 32 Patients

Almost all reports described the grafting of 2 or 3 vessels; only 2 patients received a single graft to the LAD.^4,5 The remainder involved grafts to the LAD and to the branches of the left circumflex and right coronary arteries. Most patients received a RITA graft to the LAD and SVGs to the remaining targets. The report by Poncelet and colleagues¹⁹ was notable in that the gastroepiploic artery was used as a conduit. The skeletonized and nonskeletonized use of both ITAs was reported. The ITA grafts were used as pedicles or free grafts. In only 1 case was an endarterectomy of an obtuse marginal branch performed.²⁵ When operative position was documented, more surgeons reportedly stood on the left side of the operating table than on the right (Table II).

All 32 patients survived surgery. Four developed postoperative atrial fibrillation.^1,6,20 One required a repeat sternotomy because of bleeding,²⁰ 1 had a prolonged intubation time,¹⁹ and 1 experienced irreversible renal failure.¹⁸ Among the 13 patients for whom information was available, the longest follow-up period was 5 years.¹⁹

Discussion

Dextrocardia was first described in 1606 by anatomist-surgeon Hieronymus Fabricius, and an account of SI was given in 1643 by Marco Aurelio Severinus.²⁹ In strict terms, dextrocardia refers to the condition wherein most of the cardiac mass is situated to the right of midline; the cardiac apex may or may not be on the same side. In common practice, however, most descriptions of dextrocardia refer to a cardiac mass and apex on the right. In adults, dextrocardia is usually associated with atrial SI, with the morphologic right atrium on the left side and the left atrium on the right. This finding is often concomitant with mirror-image symmetry of the bronchial branching pattern and the intra-abdominal viscera (SI totalis), with the liver on the left and the spleen on the right (Fig. 1).³⁰ Dextrocardia can occur as an isolated abnormality, although this is rare in adults who present for CABG: most reports in this surgical context mention dextrocardia that is associated with SI totalis. Cardiac anomalies in association with SI totalis are rare, whereas anomalies with isolated dextrocardia are common.³⁰

Fig. 1 Anatomic variants within the spectrum of dextrocardia. Atrial situs may be solitus (usual), inversus (SI), or ambiguus (with 2 morphologically identical atrial appendages).

ccTGA = congenitally corrected transposition of the great arteries; LAI = left atrial isomerism; RAI = right atrial isomerism; rt = right

Preoperative Evaluation

The standard preoperative evaluation of CABG patients with dextrocardia includes clinical examination, ECG, chest radiography, TTE, and coronary angiography. Clinical examination reveals a right-sided cardiac apex with a left-sided liver in the presence of SI totalis. If the main symptomatic lesion is within the region of the LAD, chest pain may be reported as anterior–right-sided.² The ECG typically shows features of mirror-image dextrocardia, with low voltages in conventionally placed anterolateral chest leads.³¹ Inverted P waves in lead I are also typical in dextrocardia with SI.^12,22,32 Particular care should be taken with ECG interpretation during attempts to identify the area of myocardium that is involved in acute coronary syndromes in patients with dextrocardia, because of the abnormal position of the heart relative to conventional ECG lead positions.³¹ Results of chest radiography confirm the position of the heart and may reveal an inverted main bronchus branch pattern, as well as a gastric air bubble beneath the right hemidiaphragm.³¹ A detailed TTE enables definition of the atrial situs and the concordance of atrioventricular (AV) and ventriculoarterial (VA) connections. Normal systemic and pulmonary venous drainage should be confirmed, and a search for intracardiac shunts should be performed. In addition, coronary artery anomalies may be seen on TTE.

Coronary angiography in patients with dextrocardia requires only minor modifications to catheter-insertion technique and in the interpretation of projections.³³ Successful percutaneous coronary intervention has been performed in patients with coronary artery disease and dextrocardia.³⁴ When ccTGA has been recognized on TTE, complete left- and right-heart catheterization can exclude intracardiac shunts, elevated ventricular end-diastolic pressures, and systemic tricuspid valve regurgitation.¹⁸

Of note, echocardiography was not performed in all 32 patients with dextrocardia. Some were evaluated with the use of thallium scintigraphy.3,10,11,14 Only 4 reports besides our own described the imaging of the abdominal viscera by plain abdominal radiography, ultrasonography, or computed tomography.4,18,19,26 The patient with situs ambiguus underwent magnetic resonance imaging of the chest and abdomen,¹⁸ and the patient with ccTGA underwent left- and right-heart catheterization.²¹ Some patients also had lung-function tests during their preoperative evaluations.^15,26 Left ventricular function was reportedly poor in 2 patients.^14,24 In most patients with SI totalis, an inverted situs of the abdominal viscera is merely to be noted after abdominal ultrasonographic or computed tomographic imaging. Clearly, atrial SI is relevant to the decision to institute CPB and to perform an ONCAB operation. It is important to know preoperatively whether patients have any coronary anomalies or coronary artery aneurysms.²⁴

Key Surgical Arrangements

Cannulation for Cardiopulmonary Bypass. In preparation for cannulation for CPB, attention should be given to the location of the aortic arch, which may be right-sided in patients with dextrocardia (Table III).³² In SI and dextrocardia, the ascending aorta is behind and to the left of the pulmonary trunk.¹⁰ If bicaval cannulation is required, the presence of bilateral superior venae cavae (SVCs) may influence the cannulation approach. An additional SVC draining to the coronary sinus is also relevant if retrograde cardioplegia is being considered for myocardial protection in ONCAB cases. One case has been reported of a CABG patient who had a single left SVC, albeit with situs solitus and levocardia.³⁵ Situs solitus in dextrocardia makes access to the right atrial appendage difficult to attain. In the rare instance of left atrial isomerism, the inferior vena cava (IVC) may drain into a left SVC, as is discussed below.¹⁸ In right atrial isomerism, there may be anomalous pulmonary venous drainage, and in both types of situs ambiguus, the atrial septum may be incompletely formed.³⁰ Furthermore—although the situation is not described in regard to adult patients with dextrocardia who need CABG—adults may present with atrial septal defects. These defects should probably be closed at the time of CABG. This would warrant CPB and bicaval cannulation with caval snares.

TABLE III. Surgical Implications of Anatomic Variants in Dextrocardia

Exposure of Surgical Targets. The exposure of surgical targets for CABG in dextrocardia patients may be difficult with a conventional operative arrangement. Most reported operations (and our own 2) were performed while the surgeon stood on the left side of the operating table. This position facilitates grafting to vessels in both coronary artery distributions and particularly to the circumflex region, which is exposed by retracting the heart toward the surgeon on the left side of the table. The LAD anastomosis can probably be performed with similar ease from either side of the table. Because the right ventricle (RV) is on the left and anterior to the LV, exposure of the right coronary branches is perhaps easier from the left side. If the surgeon stands on the left side, the position of the stabilizer/retractor device for OPCAB grafting may also need to be modified.²⁷

Choice of Conduits and Graft Configuration

The choice of conduits is clearly important when any CABG is performed, but in patients with dextrocardia it is even more crucial due to the position and rotation of the heart. In early reports of CABG in dextrocardia patients, SVGs were used exclusively.^1-3 The 1st use of an ITA (the RITA) was reported in 1988.⁴ In CABG for patients who have normal cardiac anatomy and levocardia, the long-term patency rate of the LITA–LAD graft makes the LITA the conduit of choice for this anastomosis.³⁶ In dextrocardia, however, the RV is on the left of and anterior to the LV, and the LAD emerges from the right side of the aorta and courses along the interventricular groove toward the right hemithorax.^10,19 Accordingly, the LITA may be too short to revascularize the LAD even when dissected beyond its bifurcation.¹⁹ In contrast, the RITA may be more suitable because of its proximity to the rightward course of the LAD, particularly for distal lesions that can be bypassed without anastomotic tension.^10,19 More-distal LAD lesions may be bypassed by use of full skeletonization to harvest the LITA.^16,26

In 4 patients, both ITAs were harvested, and these were used in varying combinations of free and pedicled grafts, either skeletonized or nonskeletonized.8,16,19,27 If the LITA is too short to graft to the LAD, it can still be used to revascularize the circumflex region by passing it through the transverse sinus.¹⁹ In 4 patients, the radial artery was used as an additional arterial conduit.12,16,26,27 In 1, the gastroepiploic artery was used as an in situ pedicled graft for a right coronary target on the inferior diaphragmatic surface of the heart, which it could easily reach when passed anteriorly through the diaphragm.¹⁹ Naik and colleagues¹⁰ observed that, because the obtuse marginal vessels are more anterior in dextrocardia, a shorter conduit is required for revascularization. Therefore, arterial grafts may be more suitable, because they are less likely to kink than are SVGs.

Rare Anatomic Variants

Two cases merit further comment. One is that of the patient with situs ambiguus,¹⁸ which refers to atrial isomerism, with either 2 morphologic left atria or 2 morphologic right atria (Fig. 1). In the reported case, left atrial isomerism was present. This condition is associated with polysplenia and, importantly, with a midline liver and abnormal IVC drainage—in many cases, with IVC interruption and drainage to one of the atria through the hemiazygos veins.³⁰ This has clear implications in terms of venous cannulation in ONCAB procedures (Table III). In addition to abnormalities in systemic venous drainage, such as in left atrial isomerism, some patients may have at least partial anomalous pulmonary venous drainage. This is valuable information with which to be armed before CABG, although if there is a single anomalous pulmonary vein, it may not require redirection. Cobiella and coworkers¹⁸ performed magnetic resonance imaging to define the infra-diaphragmatic systemic venous drainage in their patient—a seemingly prudent action if 2 morphologically identical atria are seen on preoperative TTE.

The 2nd case of particular interest is that of the patient with ccTGA.²¹ Many patients with ccTGA survive into adulthood without symptoms.³⁷ The heart in ccTGA has both AV and VA discordance and may be concomitant with atrial situs solitus or SI.³⁰ Dextrocardia is often present, in which case the morphologic RV is the systemic ventricle. Of note, the RV is much more hypertrophic than usual, working at systemic pressures although perhaps with a more diminutive coronary arterial supply. This places the systemic RV at even greater risk of ischemia than the normal systemic LV.²¹ The ccTGA might be associated with impaired function of the systemic RV, important tricuspid valve regurgitation, and late-onset heart block.³⁷ It is therefore advisable that these patients undergo both left- and right-heart catheterization.²¹ Patients with AV discordance have a high incidence of coronary arterial anomalies in addition to anomalous coronary venous return, which are both of clear importance in CABG (Table III).³⁸

Summary

Important anatomic variants in dextrocardia patients have considerable surgical implications: great-vessel relationships; the side on which the aortic arch is located; atrial situs; systemic, pulmonary venous, and coronary sinus drainage; AV and VA concordance; and coronary arterial anatomy. Patients with dextrocardia require special preoperative evaluation, selective intraoperative approaches in terms of cannulation and choice of conduits, and graft placement and configuration that relate appropriately to the abnormal position and rotation of the heart. Finally, the increasing population of patients with adult congenital heart disease³⁹ represents a new group of potential CABG patients in whom dextrocardia may be present and to whom these considerations might apply. These patients may experience good outcomes if the surgical implications of anatomic variants in dextrocardia are appropriately considered.