Transient Electrocardiographic Changes Simulating Myocardial Infarction in Pneumonia of the Aged

Electrocardiographic changes simulating acute anteroseptal myocardial infarction were observed in 12 aged patients with pneumonia. The electrocardiographic changes were consisted of QS patterns or decreasing r amplitudes in V1 through V3 or V4 with monophasic ST elevation and terminal T inversion. These changes appeared in conjunction or slightly delayed with the onset of pneumonia. The Q waves disappeared with the recovery from the pneumonia by about 7 days, while the negative T lasted for about a week to one month. Eight cases were autopsied and no anteroseptal myocardial infarctions were disclosed. The major clinical findings were dyspnea, cough, sputum, cyanosis, consciousness disturbances, and no anginal pain was observed. The pneumonia was extended more than two lung lobes and associated with pleural effusion or adhesive scars. In laboratory examination GOT elevated slightly in 4 cases. BUN elevated transiently in seven cases and CRP was strongly positive in all cases. Arterial PO2 decreased to less than 70mmHg and hematocrit elevated by 4 to 9% in all cases. Eight cases were autopsied. Major pulmonary findings were emphysema in six cases, bronchitis in seven cases and pneumonia in six cases. A case of old myocardial infarction in the posterior wall and a case of subepicardial hemorrhage in the posterior wall were observed, but no anteroseptal intarction was found in all cases. More than 50% of coronary stenoses in the left anterior descending branch were found in seven cases, and small myocardial scars were disclosed in five cases. The mechanisms responsible for the electrocardiographic changes simulating myocardial infarction might be attributed to the posterosuperior deviation of QRS axis from the chronic lung diseases, acute right heart overloading, hypoxia, coronary sclerosis, and the elevation of hematocrit as well as blood viscosity in acute pneumonia. Disturbances in myocardial microcirculation and oxygen supply as well as pulmonary factors were postulated.