Clincial Complications And Diagnosis Of Acute Myocardial Infarction
In the majority of cases, acute myocardial infarction is accompanied by complications and in many cases these account for mortality.
Arrhythmias: Several arrhythmias develop. These include frequent ventricular ectopics, ventricular tachycardia, ventricular fibrillation, sudden cardiac arrest, atrial fibrillation and several grades of heart block. Fatal arrhythmias such as ventricular fibrillation and cardiac arrest are more prone to develop in the presence of bradycardia, especially during the first few hours after onset. With the passage of time, this risk comes down.
Cardiac Failure: This may take the form of acute left ventricular failure or congestive cardiac failure.
Cardiogenic shock: Infarction of 40% or more of the ventricular myocardium leads to cardiogenic shock. If the shock is not relieved by the usual measures, mortality exceeds 50-80%.
Pericarditis: This develops in 15-20% of patients, 24-36 hours after the onset of the infarction. It is seen in full thickness infarcts. It subsides spontaneously without further complications.
Phlebothrombosis and Pulmonary Embolism: These develop as a result of prolonged recumbency, venous stasis and tendency for venous thrombosis.
Arterial Embolism: Mural thrombi develop on the infracted endocardium and these may embolise into arterial trunks. This risk starts a day or two after the infarction and persists for a few weeks.
Papillary Muscle Dysfunction and rupture: Ischemia and infarction of the papillary muscles lead to mitral regurgitation. Rupture of the papillary muscles results in the development of acute mitral incompetence which tips the patient into acute cardiac failure.
Cardiac rupture: This may develop by the third to the fifth day. The infracted area gives way giving rise to hemopericardium, cardiac tamponade and death in the majority of cases.
- Cardiac aneurysm: Weakening of the scar leads to bulging out of the ventricle and the development of ventricular aneurysm. The common sites are the anterior and apical regions. This leads to persistent congestive failure, recurrent embolism and ventricular tachycardia. On palpation of the precordium, the aneurysm can be felt as a see-saw pulsation in relation to the apex beat. The condition can be confirmed by X-ray examination, echocardiography and angiocardiography.
- Dessler’s syndrome: This is probably an immune-mediated reaction in which pericarditis, pleurisy, fever, arthritis and elevation of ESR develop 1-6 weeks after the infarction.
Diagnosis On ECG
S-T Elevation On ECG
Myocardial infarction is a serious disease with an overall immediate mortality ranging up to 25%. Maximum mortality is in the first 6 hours of onset, and death is due to fatal arrhythmias (Ventricular fibrillation or cardiac arrest) or other complications such as shock and cardiac failure. For the first six months after infarction, the risk of developing sudden death is still high, but this risk falls after this period. Anterior infarction carries a grave prognosis if accompanied by conduction disturbances. All the major complications worsen the prognosis. Age above 70 years, hypertension, diabetes mellitus and heavy cigarette smoking worsen the outlook further.
© 2014 Funom Theophilus Makama