INTRACARDIAC ECHOCARDIOGRAPHIC IMAGING OF THE LEFT-VENTRICLE FROM THERIGHT VENTRICLE - QUANTITATIVE EXPERIMENTAL EVALUATION

Purpose: Our purpose was to demonstrate that intracardiac ultrasound i maging from a transducer placed in the right ventricle can be used to quantitatively image the left ventricle in a swine model. Background: The left ventricles and right ventricles of dogs and human beings have been studied with intracardiac echocardiography. Usually intracardiac echocardiography has been performed with the ultrasound catheter in t he chamber being studied because of limited depth of field. Thus left ventricular imaging required that the ultrasound catheter be placed in tra-arterially and manipulated into the left ventricle. The availabili ty of lower frequency ultrasound catheters may allow left ventricular imaging from the right ventricle-a more clinically attractive approach . Method: In 10 closed chest swine, a 10F, 10-MHz ultrasound catheter was placed into the right ventricle through an introducer sheath place d in the right internal jugular vein. Two-dimensional transthoracic ec ho images were obtained for comparison. Two protocols were used to ima ge global left ventricular function and regional wall motion during ph armacologic challenge. In protocol 1 (n = 4) we evaluated global left ventricular performance in response to interventions: dobutamine, halo thane (a myocardial depressant), nitroprusside, and volume loading. In protocol 2 (n = 6) we evaluated regional contraction abnormalities in duced by coronary arterial balloon inflation and deflation (reperfusio n) and dobutamine. At baseline and after each intervention, global fun ction of the right ventricle and left ventricle was measured as cross- sectional end-diastolic area and end-systolic area, and regional contr action was evaluated as the percentage of left ventricular circumferen ce with a wall motion abnormality. Intracardiac pressures and cardiac output were also measured for comparison. Left ventricular cross-secti onal area ejection fractions (area EF) were calculated for both intrac ardiac and transthoracic echo images as (end-diastolic cross-sectional area - end-systolic cross-sectional area)/end-diastolic cross-section al area. Results: The 10F, 10-MHz intracardiac ultrasound catheter suc cessfully imaged the left ventricle from the right ventricle in all 10 swine. In protocol 1, dobutamine increased area EF from a baseline of 0.60 +/- 0.03 to 0.87 +/- 0.04 (P < .05). When dobutamine was added t o the myocardial depressant halothane, left ventricular area EF increa sed from a baseline of 0.55 +/- 0.03 to 0.68 +/- 0.04. In protocol 2, coronary occlusion resulted in a detectable regional wall motion abnor mality (circumferential percentage) of 23% +/- 3%. After reperfusion a nd during dobutamine stimulation, the wall abnormality decreased to 12 % +/- 4%. Transthoracic echocardiography correlated well with these in tracardiac findings. Conclusions: The left ventricle can be quantitati vely imaged from the right ventricle with the use of a 10F, 10-MHz int racardiac catheter in swine. This system can detect changes in global and regional left ventricular systolic function This technique warrant s evaluation in clinical applications.