Acute myocardial infarction--the angiographic picture: new insights into the pathogenesis of myocardial infarction

Chest pain with ST segment elevation in a patient with prosthetic aortic valve infective endocarditis: a case report

INTRODUCTION

Acute ST-segment elevation myocardial infarction secondary to atherosclerotic plaque rupture is a common medical emergency. This condition is effectively managed with percutaneous coronary intervention or thrombolysis. We report a rare case of acute myocardial infarction secondary to coronary embolisation of valvular vegetation in a patient with infective endocarditis, and we highlight how the management of this phenomenon may not be the same.

CASE PRESENTATION

A 73-year-old British Caucasian man with previous tissue aortic valve replacement was diagnosed with and treated for infective endocarditis of his native mitral valve. His condition deteriorated in hospital and repeat echocardiography revealed migration of vegetation to his aortic valve. Whilst waiting for surgery, our patient developed severe central crushing chest pain with associated anterior ST segment elevation on his electrocardiogram. Our patient had no history or risk factors for ischaemic heart disease. It was likely that coronary embolisation of part of the vegetation had occurred. Thrombolysis or percutaneous coronary intervention treatments were not performed in this setting and a plan was made for urgent surgical intervention. However, our patient deteriorated rapidly and unfortunately died.

CONCLUSION

Clinicians need to be aware that atherosclerotic plaque rupture is not the only cause of acute myocardial infarction. In the case of septic vegetation embolisation, case report evidence reveals that adopting the current strategies used in the treatment of myocardial infarction can be dangerous. Thrombolysis risks intra-cerebral hemorrhage from mycotic aneurysm rupture. Percutaneous coronary intervention risks coronary mycotic aneurysm formation, stent infections as well as distal septic embolisation. As yet, there remains no defined treatment modality and we feel all cases should be referred to specialist cardiac centers to consider how best to proceed.

Localization of culprit lesions in coronary arteries of patients with ST-segment elevation myocardial infarctions: relation to bifurcations and curvatures

BACKGROUND

Although culprit lesions in ST-segment elevation myocardial infarction (STEMI) cluster in the proximal coronary arteries, their relationship to bifurcations and curvatures, where blood flow is disturbed, is unknown. We hypothesized that (a) culprit lesions localize to disturbed flow distal to bifurcations and curvatures and (b) the distribution of culprit lesions in the left (LCA) and right coronary arteries (RCA) and resulting infarct size are related to the location of bifurcations and curvatures.

METHODS

Emory University's contribution to the National Cardiovascular Data Registry was queried for STEMIs. Using quantitative coronary angiography, the distances from the vessel ostium, major bifurcations, and major curvatures to the culprit lesion were measured in 385 patients.

RESULTS

Culprit lesions were located within 20 mm of a bifurcation in 79% of patients and closer to the bifurcation in the LCA compared with the RCA (7.4 ± 7.3 vs 17.7 ± 14.8 mm, P < .0001). Of RCA culprit lesions, 45% were located within 20 mm of a major curvature. Compared with those in the RCA, culprit lesions in the LCA were located more proximally (24.4 ± 16.5 vs 44.7 ± 28.8 mm, P = .0003) and were associated with larger myocardial infarctions as assessed by peak creatine kinase-MB (208 ± 222 vs 140 ± 153 ng/dL, P = .001) and troponin I (59 ± 62 vs 40 ± 35 ng/dL, P = .0006) and with higher in-hospital mortality (5.2% vs 1.1%, P = .04).

CONCLUSIONS

In patients with STEMI, culprit lesions are frequently located immediately distal to bifurcations and in proximity to major curvatures where disturbed flow is known to occur. This supports the role of wall shear stress in the pathogenesis of STEMI.

[A case report of an acute myocardial infarction with simultaneous occlusion of circumflex and right coronary artery]

Acute myocardial infarction due to simultaneous occlusion of two major coronary arteries is a rare phenomenon. We report a case of a 53-year-old man with many cardiovascular risk factors, who presented to the emergency with an acute coronary syndrome with ST segment elevation in anterior and inferior leads, complicated by atrioventricular block and cardiogenic shock. The coronary angiogram showed proximal occlusion of left circumflex artery and right coronary artery. Both arteries were treated successfully with thrombectomy followed by coronary stent implantation. Some similar cases have been reported, but the exact physiopathological mechanism is unknown. There is no clear strategy established for the therapeutic coverage, however, percutaneous revascularisation seems to be actually appropriated treatment.

Changing paradigms in thrombolysis in acute myocardial infarction

Acute myocardial infarction occurs when a ruptured coronary artery plaque causes sudden thrombotic occlusion of a coronary artery and cessation of coronary artery blood flow. This paper reviews the underlying coronary pathology in progressive coronary atherosclerosis, mechanisms of plaque rupture and arterial occlusion and the time relationship between coronary occlusion and myocardial necrosis. Reperfusion can be achieved by chemical thrombolysis with different thrombolytic agents. Early lysis is achieved best by prehospital administration, a transtelephonic monitor, a mobile intensive care unit, active general practitioner treatment or by warning the emergency room of impending arrival of a patient. Thrombolytic therapy may be unsuccessful and not achieve Grade III TIMI flow in less than 4 h (or even 2 h) due to inadequate or intermittent perfusion or reocclusion. Adjuvant therapy includes aspirin and platelet receptor antagonists. Bleeding is a constant danger. Direct percutaneous transluminal coronary angioplasty (PTCA) may be as effective or better than chemical thrombolysis. Reperfusion protects the myocardium and salvages viable tissue. It also improves mechanical remodelling of the ventricle. Long-term follow-up has shown that quantum leaps of fresh coronary occlusion causes step-wise progression in patient disability and that further early, prompt reperfusion can salvage myocardium and prevent this inexorable progress of the disease.