Complete heart block as an initial presentation of aortic dissection.

We report a case emphasizing the importance of including type A acute aortic dissection in the differential diagnosis of patients presenting with compete heart block, where emergent surgery is the treatment of choice and any delay in diagnosis and treatment can be catastrophic.

Introduction

Aortic dissection is a relatively uncommon disease with incidence of 2.6–3.5 per 100,000 person-years which usually presents with sudden onset of severe chest or/and back pain. Classification schemes of aortic dissection consist of the DeBakey types and the more commonly used Stanford classification. Within the DeBakey system, type I denotes a dissection that involves the full span of the aorta; type II, a dissection from the aortic root through the level of the origin of the innominate artery; and type III, a dissection from the descending aorta to the aortic bifurcation. Dissections in the Stanford classification are categorized based on the involvement of the ascending aorta (type A) or the lack of such involvement (type B). Ascending aortic dissection (AAD) may be associated cardiac tamponade, hemothorax, neurological deficit, stroke, Horner's syndrome and rarely complete heart block due to right coronary artery (RCA) occlusion. There are very few case reports of aortic dissections presenting initially as complete heart block.

Case report

A 41-year-old African American male with past medical history of hypertension presented to the ED with chest pain and transient loss of consciousness. EKG done in the ED (Image 1) showed complete heart block with ischemic ST segment depression in lateral leads (V4–V6, I, aVL). On examination, patient was diaphoretic with heart rate of 45 min–1 and blood pressure of 137/81 with a benign cardiac exam. Initial set of cardiac enzymes and chest X-ray were normal. Cardiac catheterization lab was activated emergently due to ischemic EKG changes and ongoing chest pain not responding to medical therapy. Aortogram showed ascending aortic dissection flap extending proximally into the aortic root (Image 2; Image 3) and patient was transferred emergently to operating room.

Image 1

EKG showing complete heart block with ischemic ST segment depression in anterolateral precordial leads (V1–V6) and lateral leads (I, aVl).

Image 2

Aortogram in LAO caudal projection with dissection flap.

Image 3

Aortogram in RAO-caudal projection with dissection flap.

Intraoperative findings revealed aortic dissection at level of innominate, carotid and subclavian arteries with extension into RCA. Patient was placed on cardio-pulmonary bypass and deep hypothermic arrest with retrograde cerebral perfusion. The aortic dissection was resected and re-approximated using dacron tube graft and Bio-glue. The RCA was bypassed using saphenous venous graft. Peri-operative course was complicated by prolonged cardiac arrest (pulseless electrical activity) secondary to right ventricular failure leading subsequently to multi-organ failure requiring multiple ionotropic agents. Neurological exam on day 7 revealed absence of brain stem reflexes with confirmation of brain death by cerebral perfusion imaging.

Discussion

Type A aortic dissection is an uncommon disease with high mortality rate. Typically symptoms include chest pain with radiation to the back and scapular regions. However it can mimic other cardiovascular emergencies such as acute coronary syndromes (ACS), pulmonary embolism, aortic root abscess resulting delay in definitive diagnosis and treatment, which is associated with increase in mortality. About 50% of type A aortic dissections are associated with ST-T wave changes, which serve as poor prognostic marker. Complete heart block is very rare presentation of AAD, in large retrospective study by Kosuge et al. where they evaluated 233 patients with type A aortic dissection only 1 case with ST-T wave changes was associated with complete heart block.

The pathophysiology has been described as rupture of a dissecting hematoma into the aorto-atrial space, which then extends through the interstitial tissue of the atrial myocardium and progresses down the inter-atrial septum to an area near atrioventricular node and the bundle of His. Hemorrhage then into the AV node can result in varying degrees of heart block. Rarely progression of an aortic dissection down the right coronary artery can result in complete heart block as seen in our case.2, 4

Our patient initially presented with chest pain and ischemic EKG changes with complete heart block. Decision to take patient to catheterization lab was made as the team suspected acute inferior-lateral wall MI leading to complete heart block. This case emphasizes the importance of considering differentials other than ACS in a patient presenting with ischemic changes and complete heart block on EKG. Aortic dissection is an important differential and diagnosis is often delayed when it presents with ischemic changes on EKG. Many studies have shown that ACS-like ST-T changes at presentation are a risk factor for delayed diagnosis in patients with AAD. Hansson et al. in large retrospective study also reported that nearly 1/3 of 133 patients who later underwent surgery for type A AAD were initially given misdiagnoses of ACS.

Computerized tomography (CT), trans-esophageal echocardiography (TEE), magnetic resonance imaging (MRI), and aortography are all good imaging modalities for diagnosing AAD. CT is most commonly used modality. The sensitivity of CT scanning is 93% for both type A and type B AAD. Bedside echocardiography can be utilized to detect wall motion abnormalities, dissection flap with aortic regurgitation to hasten the diagnosis, however has poor sensitivity (60%) and is limited by around the clock availability of skilled physicians. In our patient CT and Echo were not done because of sudden clinical deterioration of patient requiring emergent cardiac catherization to rule of acute inferior wall MI. In cases of type A aortic dissection surgery is the treatment of choice and delay in definitive diagnosis and treatment are major contributing factors of a high mortality rate despite significant progress in surgical treatment methods. Despite effective surgical intervention, a mortality rate of 10–35% is seen at even the best centers. Type A AAD is a highly lethal condition with a mortality rate of 1–2% for every hour after onset. At 24 h after presentation, medical management alone carries a mortality rate of 20%; at 48 h after presentation, 30%; and at 1 month, greater than 50%.