Hybrid Coronary Revascularization in Congenital Pericardial Absence: A Case Report

Introduction

First described in 1599, congenital pericardial agenesis (CPA) is a rare but well-recognized finding that occurs in 0.007% to 0.044% of the population, according to autopsy reports and surgical case series [1]. Embryologically, CPA is theorized to arise from premature involution of the left common cardinal vein, failure of fusion of the pleuropericardial membranes before heart enlargement, or a traction-induced tear in the pleuropericardial membrane during development. An estimated 33% to 50% of cases are associated with additional congenital anomalies of the thorax, including septal defects, tetralolgy of Fallot, pectus deformities, and diaphragmatic hernias [2]. In the case of isolated congenital absence of the pericardium, pure left-sided defects appear to be the most common manifestation, although foramen-type defects, right- and anterior-sided defects, and absence of the entire pericardium have also been reported [3]. The rarity of right-sided defects may be related to the relative importance of the right common cardinal vein, which develops into the superior vena cava. Most cases of CPA are asymptomatic, but patients can also present with atypical chest pain, palpitations, syncope, or dyspnea. Rarely, sudden death via cardiac strangulation through a partial pericardial defect can occur [4]. These patients may present with concomitant coronary artery disease, and several case studies have described the challenges of performing coronary artery bypass grafting (CABG) based on the abnormal anatomy described above [5,6]. Most importantly, extreme cardiac malposition can interfere with identifying and accessing important anatomic structures, including anastomosis targets.

Case Report

A 48-year-old man with a past medical history of tobacco use and no regular medical care presented to the Emergency Department with sudden-onset central chest pain radiating to the left arm, as well as concomitant nausea and vomiting. Initial workup revealed an elevated high-sensitivity troponin level of 4319 ng/L (reference range: 3–57 ng/L) and T-wave inversions in the anterior lateral leads, consistent with a non-ST elevation myocardial infarction. Additional laboratory test results revealed the presence of severe untreated type 2 diabetes mellitus and dyslipidemia. Notably, on physical examination, the patient had a significant pectus carinatum deformity.

Initial imaging with transthoracic echocardiogram was technically limited due to a leftward displacement of the heart in the patient’s chest. Cardiac catheterization demonstrated an abnormally rotated heart, with right-dominant circulation and severe coronary artery disease in the left anterior descending, first diagonal, left circumflex, and right main coronary arteries (Figure 1). The patient’s abnormal cardiac orientation on cardiac catheterization and transthoracic imaging prompted a workup for suspected congenital cardiac disease.

Cardiac MRI again revealed severe leftward rotation of the heart and suspected congenital absence of the pericardium (Figures 2, 3). Additionally, an aberrant right subclavian artery was found arising as a fourth vessel from the aortic arch. Decreased anterior wall motion consistent with a left anterior descending artery infarct was also noted. Biventricular function was otherwise normal, and no significant valvular disease was found. Given the patient’s multivessel coronary artery disease, he was referred for CABG.

On the day of surgery, the induction of anesthesia was uneventful; however, the pre-bypass transesophageal echocardiogram (TEE) examination was technically challenging. The leftward rotation and displacement of the heart in the chest required off-axis imaging, often fusing non-standard imaging windows. Normal bi-ventricular function was again confirmed, without the presence of any regional wall motion abnormalities. TEE was able to visualize a component of the right pericardium, but none was seen on the left (Figure 4). The patient’s pectus carinatum deformity coupled with an unusually wide manubrium complicated the left internal mammary artery (LIMA) harvest, as the artery was laterally displaced and densely adherent to the chest wall. However, it was able to be harvested as a pedicle graft. After sternotomy, the presence of pericardium on the right side of the heart and absence over the left side was confirmed. The lack of left-sided pericardium allowed the heart to shift leftward into the chest cavity (Figure 5). In addition, fibrous tissue was located on most of the epicardial surface of the heart. These changes complicated the surgical dissection and identification of the phrenic nerves, as they were not in their normal anatomic location. Ultimately, the case proceeded without identification of the nerves. The patient was initiated on cardiopulmonary bypass, without complication.

The case proceeded with a LIMA graft to the mid-left anterior descending artery and a saphenous vein graft to the first diagonal vessel. The only right coronary artery target that was identified was a 1-mm acute marginal on the right ventricular free wall, which was too small to be successfully grafted. Attention was turned to the inferolateral wall, but again, no suitable vessels were found. The obtuse marginal was identified in preoperative imaging as a potential target. However, the heart could not be lifted enough intraoperatively to identify an effective anatomic graft pathway, due to its posterior positioning. At that time, the decision was made to pursue a hybrid procedure with the Interventional Cardiology Department and stent the left circumflex lesion postoperatively with reliance on collateral flow to the posterior descending artery.

Immediately after bypass, there were left lateral wall motion abnormalities and right ventricular dysfunction detected on TEE. There was also inferior wall ischemia detected on the electrocardiogram, with associated posterior leaflet restriction and worsening mitral regurgitation on TEE. These findings, while concerning, were unsurprising given the incomplete revascularization of the heart at that time; an intra-aortic balloon pump (IABP) was placed as a temporizing measure. With the IABP augmenting coronary perfusion, nitroglycerine for ino-dilation, and epinephrine and dobutamine for inotropic support, the patient’s biventricular function, mitral regurgitation, and ischemic electrocardiogram changes normalized. The patient was successfully transferred to the Intensive Care Unit in stable condition.

The following morning, the patient returned to the Cardiac Catheterization Lab for percutaneous intervention. A 3×15-mm drug eluting stent was placed in the ostial left circumflex, followed by a 2.25×30-mm drug eluting stent in the first obtuse marginal. The IABP and vasoactive infusions were weaned, and the patient was extubated following stent placement. The remainder of the postoperative course was uneventful, and he was ultimately discharged home on postoperative day 7.

Discussion

The above patient presented with severe multivessel coronary artery disease and was incidentally found to have a congenital absence of the left half of his pericardium. Associated with the missing left-sided pericardium, the heart was dramatically shifted deep into the left chest, where surgical and nonsurgical approaches were needed to ultimately restore coronary perfusion and normal cardiac function. This resulted in an unplanned pseudo-hybrid coronary revascularization. The surgical limitations in caring for these patients are unique. Difficulties identified in previous surgical reports have included abnormal phrenic nerve location and division [7,8], positioning of the lung with respect to the LIMA graft in bypass surgery [9], increased risk of cardiac injury during placement of retrosternal bars [10], and lateral positioning of the graft during heart transplant, to avoid instability and twisting of the great vessels [11]. Preoperative planning for these patients should include multiple imaging modalities to characterize the missing pericardium itself, any potential associated anatomical variants previously discussed, as well as the exact position and orientation of the heart within the thoracic cavity. Cardiac MRI is generally considered the criterion standard for diagnosis [12], with echocardiography necessary to investigate dynamic function of the heart. This workup can also influence the decision to pursue a particular surgical approach. Prior case studies have discussed the benefits and limitations of on-pump versus off-pump techniques [13,14]. An off-pump approach better demonstrates the natural lie of the heart in the thoracic cavity for anastomosis planning, where cardio-pulmonary bypass allows for more access to difficult to reach targets in an empty heart. However, significant manipulation of the heart’s position within the thoracic cavity during bypass raises concern for “bowstring” phenomena and anastomosis patency when the heart shifts back to its natural position during refilling and lung insufflation. An on-pump, arrested technique was selected in this case. Unfortunately, even with manipulation of the heart, suitable targets on the inferolateral and right ventricular free wall were unable to be located despite anticipated anatomy from catheterization and cardiac imaging. Therefore, the decision was made intraoperatively to pursue a hybrid technique.

Hybrid coronary revascularization is a well-characterized technique combining the minimally invasive CABG technique with percutaneous coronary intervention (PCI) for good outcomes based on the theory that the combination of the two leads to an earlier recovery and fewer complications [15]. While this surgery was not minimally invasive, the complimentary use of PCI was paramount to reach the inaccessible parts of the heart for revascularization. If a patient is known to have severe cardiac anatomical variations, it may be wise to get the Cardiology Department involved early in the preoperative planning process to allow for bridging contingencies, like IABPs and staged procedures. These preparations were not made in this case but may have expedited the PCI following CABG, rather than waiting until the following day.

Conclusions

This case demonstrates the potential complications wrought by an absent pericardium and the utility of incorporating complementary modalities for restoration of cardiac function in the presence of deranged anatomy when there are limitations imposed on CABG. Early multispecialty coordination and consideration of these complimentary interventions is highly recommended.