Abstract
Spontaneous coronary artery dissection is a rare but important differential diagnosis in fit young women presenting with chest pain.
Introduction
Coronary artery dissection occurs when blood enters a false lumen in the tunica media through an intimal tear, causing restriction of blood flow in the true lumen, thereby leading to myocardial ischaemia. The pathogenesis is incompletely understood. This condition commonly presents with typical angina type chest pain, often with malignant arrhythmias, including ventricular fibrillation. Cardiac enzyme release and ischaemic ECG changes are often present. Spontaneous coronary artery dissection (SCAD) is associated with mortality as high as 20% in some reports. 1
Coronary artery dissection is usually associated with type A aortic dissection, coronary angiography/intervention, chest wall trauma or coronary artery surgery. However, SCAD occurs in the absence of any of these precipitating factors.
Diagnosis is made by coronary angiography, often assisted by intravascular ultrasound (IVUS). Management of SCAD consists of conservative management, antithrombotic therapy, coronary intervention with the deployment of intra-coronary stents or coronary artery bypass grafting (CABG).
Case report
A 38-year-old Caucasian woman, with no significant medical history apart from a progesterone-secreting intrauterine device, was admitted to hospital for primary percutaneous coronary intervention with sudden onset of chest pain. She was the mother of two children, aged 5 and 2 years. ECG, during transit to hospital, showed ST elevation in anterior leads. She sustained a ventricular fibrillation cardiac arrest which was successfully cardioverted.
Coronary angiography showed a normal left main stem, circumflex and right coronary arteries. There was a discrete lesion of 70% severity, in the mid left anterior descending (LAD) artery, extending to the bifurcation with the second diagonal, resembling a dissection (Figure 1A). IVUS confirmed a false lumen, containing haematoma, and compression of the true lumen (Figure 1B). Echocardiography showed satisfactory left ventricular function with hypokinetic apical and septal segments. The ST segments stabilized and she became pain-free. The patient was managed with aspirin, clopidogrel and low-molecular-weight heparin. The Troponin I following admission was 4300 ng/L (0–50).
Second angiogram showing the propagation of the dissection.
Discussion at a multidisciplinary meeting led to a decision to repeat the coronary angiogram 4 days later. On repeat angiography, the dissection was seen to extend proximally along the LAD (Figure 2). During angiography, the patient became hypotensive with ST elevation and suffered a cardiac arrest, but successfully resuscitated. Emergency CABG was performed using the left internal mammary artery (LIMA) to the LAD and saphenous vein graft to the diagonal branch with cardiopulmonary bypass (CPB) at 35°C using a single dose of anterograde cold blood cardioplegia. The LAD was opened in its mid-section where the external appearance implied it was intact; however, after arteriotomy it was found that the dissection was extensive. The LIMA was anastamosed to the LAD taking care to approximate all dissected layers of the LAD distal to the haematoma. CPB was discontinued with no inotrope support. Cross-clamp and CPB times were 21 and 35 min, respectively. The patient was extubated on post-operative day 1 and transferred to the ward. She made a satisfactory recovery and was discharged home on day 7.
(a) Initial angiogram showing the dissection extending past the first diagonal (arrows). (b) IVUS showing the true lumen (arrow) and false lumen (bold arrow).
Discussion
The incidence of SCAD is 0.2 per 100,000 population years. However, this is thought to be an underestimation of the true incidence as SCAD is hypothesized to be a cause of sudden death where no diagnosis is found. In large multicentre studies, the incidence of SCAD has been reported to be up to 0.2% of all coronary angiograms performed.1,2 Females account for around 70% of cases and the reported mean age is between 35 and 42 years. 3 The patients tend to be fit and healthy and may be associated with progesterone-secreting intrauterine devices.
A large proportion of SCAD cases appear to occur in the peri-partum period. A number of changes occur in pregnancy which may account for this. Increased progesterone levels lead to arterial wall changes with reticulin fibre fragmentation and collagen degeneration. Elastic fibre corrugation is lost and smooth muscles undergo hypertrophy. This leads to changes in the protein content of the tunica media and inevitable weakening of the arterial wall. These changes, along with the reduced peripheral vascular resistance and increased cardiac output state of pregnancy, can predispose to intimal rupture. Other predisposing factors include severe hypertension, smoking, collagen disorders and oral contraception. 4
It is unclear how to manage patients who present with SCAD. Shamloo et al. 5 investigated 344 patients diagnosed with SCAD. Of the 156 patients who underwent conservative management, 33 (21%) had to undergo rescue invasive therapy in the form of CABG or percutaneous coronary intervention. Of the 158 patients who underwent these invasive therapies, initially only 2.5% had to have a second procedure. 5
In patients undergoing CABG, follow-up angiography has shown graft occlusion as the native vessels involved in the dissection attain good blood flow. In a study of 87 patients, 11 out of 15 conduits had become occluded after CABG. 1 Often this occurs asymptomatically. While it may be argued that the resolution of dissection may have been achieved with conservative management, CABG in these cases may be seen as essential to provide myocardial oxygenation during the acute phase of dissection prior to restoration of native coronary flow. Percutaneous coronary intervention is associated with high levels of complications such as failure to enter the true lumen, failure to pass the lesion and, most significant of all, propagation of the dissection. 1
Conclusions
SCAD is a condition most commonly found in young women. A small number of cases are associated with contraceptive use. A high level of suspicion of the disease should be maintained in order to make a fast and accurate diagnosis in any patient who is young and lacks risks factors for coronary artery disease. If coronary angiography is subsequently performed, it should be in a centre that has immediate access to surgical intervention. Management decisions should always be undertaken in the setting of multidisciplinary team meeting with both cardiothoracic surgeons and cardiologists present. However, there is incomplete evidence found in the literature to provide a definite management policy.