Reduction of left ventricular size following oxygen inhalation in patients with coronary artery disease as measured by biplane coronary cineangiograms.

Left ventricular size is one of the major determinants of myocardial oxygen consumption, therefore if oxygen inhalation reduces myocardial oxygen demand, such might be beneficial in the treatment of acute myocardial infarction. Routine diagnostic biplane left coronary cineangiograms were obtained during air or oxygen breathing in 11 patients with old myocardial infarction or angina pectoris. Coordinates of the points on the left coronary artery were measured and throughout one cardiac cycle frame by frame. The spatial distance (segment length: L) between any two of these points was calculated. Segment length at R wave on the electrocardiogram (LECG R) and minimum value (Lmin) for each segment were calculated. Arterial pO2 was elevated by oxygen breathing from 91 +/- 4 (+/- SE) to 427 +/- 18 mmHg. Left ventricular segment length was significantly reduced by oxygen breathing: LECG R being reduced following oxygen breathing from 62.3 +/- 3.0 to 60.6 +/- 3.0 mm (a decrease of 3.3 +/- 0.8%) and Lmin also being reduced from 55.9 +/- 2.8 to 54.4 +/- 2.8 mm (a decrease of 3.1 +/- 1.0%). These figures indicate that left ventricular size was reduced. Reduction in left ventricular size through oxygen inhalation, by reducing myocardial oxygen demand, should therefore be beneficial in coronary artery disease.