Acute atrial infarction: a relatively neglected and under-recognized entity in clinical practice

BACKGROUND

Electrocardiograms (ECGs) and angiographic features indicative of acute atrial infarction (AAI) often go unnoticed and are under-recognized in clinical practice.

METHODS

In this retrospective observational study, we analyzed the data of 3981 out of 9803 patients (40.61%) who were referred to our hospital for angiography and/or percutaneous coronary intervention due to acute coronary syndrome (ACS). These patients were diagnosed with acute ST segment elevation myocardial infarction (AMI) affecting the inferior, posterior, and/or right ventricular regions.

RESULTS

Of the 3981 patients, 270 (6.78%) had involvement of the main coronary atrial branch meeting the angiographic criteria for AAI. Among the 270 patients identified, the right coronary artery was diagnosed as the infarct-related artery (IRA) in 187 patients (group R), while the left circumflex artery was the IRA in 83 patients (group L). The incidence of PR-segment deviation was similar between the two groups (65.2% in group R vs. 66.3% in group L, p = 0.870), as was occurrence of atrial tachyarrhythmia (67.4% vs. 55.4%, p = 0.059). The prevalence of P wave morphology abnormalities (29.9% vs. 49.4%, p = 0.005) and sinus bradycardia or arrest (25.1% vs. 66.3%, p < 0.001) was significantly lower in Group R than in Group L.

CONCLUSION

Acute atrial infarction represents a distinct yet frequently overlooked clinical entity. Clinicians should consider the potential for atrial arrhythmias, thromboembolism, hemodynamic instability, and atrial rupture when diagnosing AAI.

Unusual case of right atrial reinfarction

It is well known that atrial infarctions are rare comparing to the ventricular. They cannot easily be verified on ECG and the standard autopsy technique does not include a detailed review of the atrial wall, so the atrial infarction often remains undiagnosed. A 63-year-old male was treated and died in an intensive care unit due to decompensated liver insufficiency and cardiac disease following long-lasting alcohol abuse. At autopsy, the extreme cardiomegaly was found, severe atherosclerosis of the anterior descending branch of left coronary artery. The posterior wall of the right atrium was thickened (cca 9 mm) in diameter of cca 3 × 3 cm, and this area was yellowish in the luminal part, while the central part was filled with dark red blood. A detailed dissection of the coronary arteries showed the complete occlusion of the atrial branch of the right coronary artery wreath as far as the place of sinoatrial artery branching, which corresponded anatomically to the described area of infarction on the posterior wall of the right atrium. Histopathological examination of the previously described area of the posterior wall of the right atrium, showed four zones of heart muscle changes: 1. zone of partially preserved structure of the heart muscle, 2. zone of cellular (immature) connective tissue, 3. areas of bleeding in cellular connective tissue, and 4. zone of acellular (old) connective tissue. These histopathological changes indicated that the posterior wall of the right atrium was affected by myocardial necrosis in at least two and possibly more times. It is reasonable to think that bleeding in the third zone of the posterior wall of the right atrium contributed greatly to the death due to the anatomical proximity to the sinoatrial node. It was confirmed by the existence of bradycardia with a prolonged PR interval, PR segment elevation in D1 and aVL lead and PR depression in the D3 lead on the ECG. These ECG changes appeared immediately before asystolia and the death of the patient, but not ventricular fibrillation or electromechanical dissociation due to ventricular infarction. The presented case shows that detailed autopsy examination of atrial wall and blood vessels can sometimes be crucial in disclosing the cause and mode of death if the ischemia and necrosis attack only the atrial wall, especially in the region of the heart conduction system.

Angiotensin II receptor blockers in the prevention of atrial fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia. While antiarrhythmic agents and electrical cardioversion are highly effective in restoring sinus rhythm, the results obtained in prevention of recurrences are disappointing. Recently, angiotensin II has been recognized as a key factor in atrial structural and electrical remodeling associated with AF. So there are several potential mechanisms by which inhibition of the renin-angiotensin-aldosterone system may reduce AF. In this review, we report the results of studies evaluating the effect of angiotensin II receptor blockers (ARBs) in various clinical settings (i.e., lone AF, hypertension, high-risk patients, congestive heart failure, secondary prevention). However, many of these studies are small and retrospective and have a limited follow-up; moreover, since AF is related to several causes, chiefly heart diseases, patients with different characteristics have often been enrolled. Thus, it is not surprising that the results obtained are frequently conflicting. With these limitations and considering only the results of larger studies with longer follow-up, ARBs are effective in preventing AF in patients with congestive heart failure or hypertension with left ventricular hypertrophy or coronary artery/cerebrovascular disease. In any case, the use of ARBs is not recommended at present in clinical practice to prevent AF.

Left atrial infarction: a case report and review of the literature

The majority of cardiac related deaths are due to ischemic heart disease, with the most common clinical scenario being severe coronary artery atherosclerosis resulting in left ventricular myocardial infarction. However, infarction of other cardiac chambers does occur, and often has specific clinical associations. We report a case of a 70-year-old man who suffered from left atrial infarction that resulted in a transmural rupture of his left atrium. The patient had a history of rheumatic heart disease, mitral valve stenosis, and severe atherosclerotic coronary artery disease. Four days before death, he underwent mitral valve replacement and left circumflex coronary artery bypass. Two days later, he developed atrial fibrillation. On the day of death, he had decreased mental status, questionable seizure activity, hematemesis, ventricular tachycardia, and eventually asystole. At autopsy, he had significant hemopericardium with a fibrinous pericarditis and bilateral hemothoraces (total blood volume: 1250 mL). A 0.1 to 0.2 cm left atrial transmural defect was identified. The prosthetic mitral valve was free of vegetations, and completely intact. Similarly, the left circumflex artery bypass graft was completely patent and unremarkable. Severe calcific atherosclerosis was of his native left circumflex and left main coronary arteries. Microscopic examination revealed acute myocardial infarction of the left atrium at the rupture site. The anatomy of atrial circulation as well as the pathology and consequences of atrial infarction are discussed.