A 47 year old man presents to the hospital complaining of palpitations. The patient repos that while cooking breakfast this morning, he felt his hea "racing in his chest" and was unable to catch his breath. He states that sitting down brought no relief. He called for an ambulance and he was brought to the emergency depament. The man has no significant past medical history and takes no medications regularly, other than ranitidine for occasional heaburn. On examination, the patient is quite thin, but well developed and in mild distress. His globes appear exophthalmic. His pulse is 140/min and irregularly irregular. There are no murmurs, and the lung examination is clear. A non-tender midline thyroid mass is palpable. Which of the following findings on his echocardiogram would suggest a diagnosis of long- standing atrial fibrillation?
High-Yield Explanation
Echocardiography is an invaluable tool for assessing cardiovascular function in both normal and disease states. In the case of atrial fibrillation (AF), a chronic course versus an acute and self-limited course poend completely different treatment strategies and long-term prognoses. The most common cause of chronic AF is valvular disease, followed by congestive hea failure (CHF). The most common anatomic correlate seen in patients with AF (Framingham Hea Study) is an enlarged left atrium. A dilated left ventricle is commonly seen with both CHF and AF. However, an enlarged left atrium is more closely correlated with chronic AF than is left ventricular dilation. The causal relationship between an enlarged left atrium and AF is unclear. A dilated right ventricle is commonly seen in severe right hea failure (RHF). The most common cause of RHF is left hea failure (LHF). There is no consistent relationship between right hea size and the presence of AF. A hyperophied ventricular septum is commonly seen in hypeensive hea disease or idiopathic hyperophic aoic stenosis. Chronic AF in these patients, however, is much less common. Ref: Prystowsky E.N., Padanilam B.J., Waldo A.L. (2011). Chapter 40. Atrial Fibrillation, Atrial Flutter, and Atrial Tachycardia. In V. Fuster, R.A. Walsh, R.A. Harrington (Eds), Hurst's The Hea, 13e.