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Purpose: Our purpose was to demonstrate that intracardiac ultrasound imaging 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 the chamber being studied because of limited depth of field. Thus left ventricular imaging required that the ultrasound catheter be placed intra-arterially and manipulated into the left ventricle. The availability of lower frequency ultrasound catheters may allow left ventricular imaging from the right ventricle-a more clinically attractive approach. Methods: In 10 closed chest swine, a 10F, 10-MHz ultrasound catheter was placed into the right ventricle through an introducer sheath placed in the right internal jugular vein. Two-dimensional transthoracic echo images were obtained for comparison. Two protocols were used to image global left ventricular function and regional wall motion during pharmacologic challenge. In protocol 1 (n = 4) we evaluated global left ventricular performance in response to interventions: dobutamine, halothane (a myocardial depressant), nitroprusside, and volume loading. In protocol 2 (n = 6) we evaluated regional contraction abnormalities induced by coronary arterial balloon inflation and deflation (reperfusion) and dobutamine. At baseline and after each intervention, global function of the right ventricle and left ventricle was measured as cross-sectional end-diastolic area and end-systolic area, and regional contraction was evaluated as the percentage of left ventricular circumference with a wall motion abnormality. Intracardiac pressures and cardiac output were also measured for comparison. Left ventricular cross-sectional area ejection fractions (area EF) were calculated for both intracardiac and transthoracic echo images as (end-diastolic cross-sectional area - end-systolic cross-sectional area)/end-diastolic cross-sectional area. Results: The 10F, 10-MHz intracardiac ultrasound catheter successfully 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 to the myocardial depressant halothane, left ventricular area EF increased 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 abnormality (circumferential percentage) of 23% +/- 3%. After reperfusion and during dobutamine stimulation, the wall abnormality decreased to 12% +/- 4%. Transthoracic echocardiography correlated well with these intracardiac findings. Conclusions: The left ventricle can be quantitatively imaged from the right ventricle with the use of a 10F, 10-MHz intracardiac catheter in swine. This system can detect changes in global and regional left ventricular systolic function. This technique warrants evaluation in clinical applications. (J Am Soc Echocardiogr 1998;11:921-8.)

Our objective was to demonstrate that right ventricular (RV) infarction could be demonstrated by intracardiac ultrasonography in a canine model. RV infarction is a common and important clinical condition in patients with myocardial infarction. Traditional methods for diagnosing RV infarction have limitations. Intracardiac echocardiography, in which an ultrasonic transducer on the tip of a catheter is placed intravenously into the RV chamber, should allow detection of RV infarction. Nine closed-chest dogs were studied. The animals were instrumented with a 10 MHz ultrasound catheter placed into the right ventricle. The right coronary artery was occluded with a balloon angioplasty catheter for 20 minutes and subsequently embolized with elemental mercury. Intracardiac ultrasound images were obtained at baseline, during balloon occlusion, and during embolization. RV cross-sectional end-diastolic and end-systolic areas were calculated and fractional area change were calculated; RV wall motion abnormalities were also evaluated. The interventricular septal thickening was also calculated. The 10 MHz intracardiac ultrasound catheter allowed visualization of much of the RV chamber and interventricular septum. The RV cross-sectional area increased with mercury embolization, which was also associated with regional wall motion abnormalities. RV end-systolic area was 1.6 cm^2 and end-diastolic area 3.9 cm^2 at baseline; these increased to 4.8 cm^2 and 6.5 cm^2 after embolization (p <0.05). Interventricular septal thickening remained unchanged. The echocardiographic features of RV infarction, which include RV dilation and RV regional wall motion abnormalities, could be demonstrated in a canine infarct model with a 10 MHz intracardiac ultrasound catheter. (J Am Soc Echocardiogr 1997;10:352-6.)