Prompt return to normal of depressed right ventricular ejection fraction in acute inferior infarction.

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Abstract
A relatively simple, bedside, radionuclide technique was developed to measure right ventricular ejection fraction. This technique uses a collimated scintillation probe (5 .times. 5 cm sodium iodide crystal) and 113mIn injected into the superior vena cava to record a right ventricular time-activity curve. The radionuclide method was validated in 34 men (14 normals, 20 with coronary artery disease) with biplane right ventriculography (r = 0.82). Using this radionuclide method right ventricular ejection fraction was measured in 26 men (average age 51 yr) with an acute transmural myocardial infarction. Right ventricular ejection fraction was initially depressed (0.40 .+-. 0.02; mean .+-. SEM [standard error of the mean]; normal 0.57 .+-. 0.01) in all of 11 men with an acute inferior infarction but returned to normal by the 3rd day in 10 of them (0.58 .+-. 0.01;). In the 15 men with an acute anterior infarction the average right ventricular ejection fraction was normal initially (0.54 .+-. 0.01;) and individually 10 of 15 had a normal ejection fraction. Left ventricular ejection fraction was initially depressed in all patients and only 4 of 34 had returned to normal at the 3rd day. Right ventricular ejection fraction apparently regularly depressed in patients with an acute inferior infarction but normal in those with an anterior infarction. Right ventricular performance rapidly improves after inferior infarction; less improvement occurs in left ventricular ejection fraction.