Coronary artery blood flow in acute pulmonary embolism

Pulmonary embolism

Pulmonary embolism (PE) remains one of the most challenging medical diseases in the emergency department. PE is a potentially life threatening diagnosis that is seen in patients with chest pain and/or dyspnea but can span the clinical spectrum of medical presentations. In addition, it does not have any particular clinical feature, laboratory test, or diagnostic modality that can independently and confidently exclude its possibility. This article offers a review of PE in the emergency department. It emphasizes the appropriate determination of pretest probability, the approach to diagnosis and management, and special considerations related to pregnancy and radiation exposure.

Diagnosis of pulmonary embolism in the coronary care unit

The clinical diagnosis of pulmonary embolism (PE) is difficult in coronary care units (CCUs) because many findings of PE are similar to those of acute coronary syndromes and heart failure. Immobilization of only 1 or 2 days may predispose to PE. Heart failure and acute myocardial infarction add to the risk. Dyspnea may be absent or occur only with exertion. The onset of dyspnea may occur over seconds to days. Orthopnea occurs with PE as well as heart failure. When the clinical probability and results of objective testing are discordant, the posttest probability of PE may be neither sufficiently high nor sufficiently low to permit therapeutic decisions. Objective scoring systems for clinical assessment have not been developed for patients in a CCU. d-dimer is likely to be of little value for the exclusion of PE in CCUs, because elevations occur with heart failure, unstable angina, and myocardial infarction. Computed tomographic pulmonary angiography with venous phase imaging of the low pelvic and proximal leg veins (computed tomographic venography) is recommended for imaging. Scintigraphy in women aged <50 years with normal or nearly normal results on chest x-ray may be the preferred imaging test to reduce the risk for radiation. Echocardiography with leg ultrasonography is a rapidly obtainable combination of bedside tests that may be useful for young patients and patients in extremis. In conclusion, the choice of diagnostic test depends on the clinical probability of PE, the condition of the patient, the availability of diagnostic tests, the risks of iodinated contrast material, radiation exposure, and cost.

Serial changes in negative T wave on electrocardiogram in acute pulmonary thromboembolism

A negative T wave is frequently observed in precordial ECG leads in patients with acute pulmonary thromboembolism. We investigated the clinical significance of negative T wave in 15 patients with acute pulmonary thromboembolism who were treated with thrombolytic agents by measuring the mean pulmonary artery pressure and ratio of right to left ventricular end-diastolic diameter using echocardiography and ECG. The study included only patients with massive acute pulmonary thromboembolism of a mean age of 65+/-9.7 years (+/-SD). A negative T wave was observed on admission in 10 patients but was later detected in 14 of the 15 patients. The mean amplitude of the negative T wave increased within 1 week then decreased after thrombolytic treatment. The peak negative amplitude of the T wave was observed from 1 to 7 days (mean, 2.6+/-1.8 days) and disappeared afterwards. During this period, improvements in both the mean pulmonary artery pressure (37.8+/-11.2 to 19.1+/-6.7 mmHg) and the ratio of right to left ventricular end-diastolic diameter (0.97+/-0.16 to 0.51+/-0.13) were noted in all patients. Our results suggest that an increase in the amplitude of negative T wave in precordial leads after thrombolytic therapy in patients with massive acute pulmonary thromboembolism reflects improvement in cardiopulmonary hemodynamics.

The electrocardiogram in acute pulmonary embolism

Electrocardiograms of 90 patients with arteriographically documented acute submassive or massive pulmonary embolism and no associated cardiac or pulmonary disease were studied. Patients were derived from the Urokinase-Pulmonary Embolism Trial National Cooperative Study. In massive embolism, the electrocardiogram was normal in 6 per cent (3 of 50) of patients. With submassive embolism, 23 per cent of patients (9 of 40) had a normal electrocardiogram. Since one or more of the traditional manifestations of acute cor pulmonale (S1Q3T3, right bundle branch block, P pulmonale, or right axis deviation) occurred in only 26 per cent of patients, one could not rely exclusively upon these electrocardiographic abnormalities for the diagnosis of pulmonary embolism. The most common electrocardiographic abnormalities were nonspecific T wave changes which occurred in 42 per cent of patients and nonspecific abnormalities (elevation or depression) of the RST segment which occurred in 41 per cent of patients. Left axis deviation occurring in 7 per cent of the patients was as frequent as right axis deviation. Low voltage QRS complexes, previously undescribed in pulmonary embolism, occurred in 6 per cent of patients. None of the patients had atrial flutter or atrial fibrillation, which appears to occur more typically in patients with pulmonary embolism who have preexistent cardiac disease. All of the varieties of electrocardiographic abnormalities disappeared in some of the patients by 2 wk. Inversion of the T wave was the most persistent abnormality. Larger defects on the lung scan or pulmonary arteriogram occurred in patients with various abnormalities on the electrocardiogram than in patients with normal electrocardiograms. The pulmonary arterial mean pressure and/or right ventricular end-diastolic pressure was significantly higher in patients with several varieties of abnormal electrocardiograms, although the partial pressure of oxygen in arterial blood, in general, did not differ from that in patients with normal electrocardiograms. These hemodynamic correlations, made for the first time in patients, suggest that acute ventricular dilatation, possibly in combination with hypoxemia, is a causative factor of the electrocardiographic changes in acute massive or submassive pulmonary embolism.