Severe hypoxemia in a patient with acute myocardial infarction

Acute right to left shunt through patent foramen ovale presenting as hypoxemia after myocardial infarction: a case report

Introduction

This is a report of a 56-year-old man who became hypoxic due to an acute right to left shunt after sustaining a myocardial infarction involving the right ventricle. This case provides the opportunity to review several key pathophysiologic concepts in the setting of acute right ventricular infarction. Although the development of an acute right to left shunt is a rare complication of myocardial infarction, it is important to recognize the diagnosis early in order to prevent life threatening or debilitating clinical sequelae that may result from tissue hypoxia and embolic events. Transesophageal echocardiography is the noninvasive study of choice to confirm the diagnosis. Treatment involves optimization of right ventricular function to minimize shunting. However, medical therapy may provide only temporary relief, and closure of the atrial septal defect should be considered if a clinically significant shunt persists.

Case presentation

A 56-year-old Caucasian man with severe aortic insufficiency presented to the emergency department for evaluation of substernal chest pain. An inferior myocardial infarction was diagnosed by the electrocardiogram and serologic markers. Cardiac catheterization revealed complete occlusion of the right coronary artery as well as a 50-75% stenosis of the left anterior descending artery. Angioplasty of the right coronary artery was performed, but immediate re-occlusion occurred. Subsequently, hypotension and severe hypoxemia developed and persisted despite intubation and mechanical ventilation with 100% oxygen. A significant right-to-left shunt through a patent foramen ovale was diagnosed by contrast transesophageal echocardiogram. Surgical intervention was required and included coronary artery bypass grafting, aortic valve replacement as well as closure of his atrial septal defect.

Conclusion

A right to left atrial shunt is a rare complication of inferior myocardial infarction with right ventricular infarction. The diagnosis should be considered in the presence of inferior myocardial infarction when hypoxemia persists despite administration of 100% oxygen. Early diagnosis and treatment are critical in order to reduce the risk of embolization and to prevent end-organ damage due to hypoxemia.

Tricuspid valvular papillary muscle rupture with intractable hypoxia: a rare complication post MI

Acute inferior ST-elevation myocardial infarction (STEMI) alone contributes to approximately 10% of in-hospital mortality due to ischemic heart disease. Right ventricular involvement occurs in 50% of patients who present with inferior STEMIs, increasing in-hospital mortality to 31%. In the setting of concomitant severe tricuspid regurgitation, acute rupture of the papillary muscles within the right ventricle should be considered in the differential diagnosis. The authors present the case of a patient with intractable hypoxia in the setting of an acute inferior STEMI complicated by rupture of the posterior tricuspid valve papillary muscle.

Study on the risk factors of postoperative hypoxemia in patients undergoing coronary artery bypass grafting

BACKGROUND

To investigate 576 patients undergoing coronary artery bypass grafting (CABG) and to evaluate independent high risk factors of postoperative hypoxemia following CABG.

METHODS AND RESULTS

The pre-, intra-, and post-operative materials in patients who had CABG performed on them from March 2004 to March 2008 in our hospital were analyzed retrospectively. The relative factors of postoperative hypoxemia were tested through descriptive analysis and logistic regression, and the independent risk factors were obtained. Among the 576 patients investigated, 156 cases suffered from postoperative hypoxemia, and the incidence rate of postoperative hypoxemia was 27.08%. Through descriptive analysis and logistic regression, the independent risk factors of postoperative hypoxemia were as follows: preoperative chronic pulmonary diseases (odds ratio (OR)=8.531, 95% confidence interval (CI) 3.136-23.210), preoperative acute myocardial infarction (OR=3.351, 95% CI 1.539-7.296), and preoperative diabetes (OR=3.108, 95% CI 1.439-6.713). Preoperative acute myocardial infarction (OR=2.091, 95% CI 1.520-4.416) is the independent risk factor during assisted ventilation after surgery, and preoperative chronic pulmonary diseases (OR=7.19, 95% CI 2.807-18.413), pre-operative diabetes (OR=3.605, 95% CI 1.631-7.967), and preoperative acute myocardial infarction (OR=3.604, 95% CI 1.518-8.543) are the 3 independent risk factors after decannulation following CABG.

CONCLUSIONS

Preoperative chronic pulmonary diseases, preoperative acute myocardial infarction, and preoperative diabetes are 3 independent risk factors of postoperative hypoxemia following CABG.