Intracardiac balloon pump for the relief of acute mitral regurgitation.

The goal of this study was to test the hypothesis whether a small balloon placed within the mitral orifice and pulsed in a synchronous manner could reduce the degree of acute mitral regurgitation. Previous experimental studies had shown that a similar balloon within the aortic orifice relieved satisfactorily aortic regurgitation. Acute mitral regurgitation was created in 14 dogs, and a catheter with a small polyurethane balloon on its distal end was introduced to the mitral ring through the left ventricular apex. The balloon was connected to a Datascope pump for intermittent, synchronous pulsation. Left atrial, left ventricular and aortic pressures were monitored. In three animals transesophageal echocardiography was used in addition to monitor the regurgitant transmitral flow with color Doppler image. Intermittent inflation of the balloon during systole decreased the maximum left atrial pressure from 31.83 mmHg +/- 3.48 mmHg to 23.16 +/- 3.3 mmHg (p < 0.001) and the mean left atrial pressure from 21.66 +/- 2.8 mmHg to 17.25 +/- 2.76 mmHg (p < 0.001). The systolic gradient across the mitral valve increased from 59 +/- 14.53 mmHg to 77.11 +/- 12.44 mmHg (p < 0.01). Transesophageal echocardiography showed an almost 50% decrease of the transmitral regurgitant flow. It is concluded that intermittent, systolic, synchronous balloon pulsation within the mitral orifice reduces the degree of experimental, acute mitral regurgitation.

On line echocardiography in evaluating left atrial changes in acute mitral regurgitation and in monitoring a catheter-mounted balloon for its correction.

The purpose of this study was to evaluate changes in the left atrial size in acute mitral regurgitation (AMR) and monitor its correction by a catheter-mounted balloon (B). In 16 dogs, pressure changes in the left atrium (LA) were related to LA size and regurgitant mitral flow after the production of AMR by severing the mitral cusps. TEE was used for evaluating LA area (ALA) and the mitral regurgitation flow area (AMRF). TEE was also used in monitoring the position of a catheter-mounted B inserted through the LV apex and positioned on the mitral ring to relieve AMR. The B was inflated during systole and deflated during diastole. The ALA increased by 4.89 +/- 1.21 cm2 (mean +/- 1 SD) (p < 0.001) after AMR, the AMRF increased by 3.01 +/- 0.85 cm2 (p < 0.001) and the mean atrial pressure (LAP) by 9.38 +/- 2.43 mmHg (p < 0.001). In all experiments the position of the B could be confirmed in the 2D image and in 4 the reduction of AMRF by the function of the B was documented by the colour flow Doppler. It is concluded that after AMR the size of the LA increases along with the increase in LA pressure and a phasically inflated balloon and its effect on AMR can be easily identified and monitored by TEE.

Effect of acute changes in aortic pressure on the coronary reserve.

STUDY OBJECTIVE: The aim was to evaluate the effect of acute changes in aortic pressure on the coronary reserve and hyperaemic response. DESIGN: Aortic pressure changes were induced either by intra-aortic balloon pumping or by the production of acute aortic regurgitation. A transient 20 s occlusion of the left anterior descending coronary artery was used as the hyperaemic stimulus. EXPERIMENTAL SUBJECTS: The experiments were performed on 19 open chest anaesthetised dogs, weight 13-32 kg. MEASUREMENTS AND MAIN RESULTS: During intra-aortic balloon pumping the mean diastolic aortic pressure increased by 24.7(SEM 2.9) mm Hg (p less than 0.001), while in aortic regurgitation it decreased by 47.7(11.1) mm Hg (p less than 0.01). At the peak hyperaemic response the driving coronary pressure was 121.4(2.8) mm Hg during intra-aortic balloon pumping and 59.8(11.5) mm Hg during aortic regurgitation. The peak hyperaemic flow increased by 12.0(3.8) ml.min-1 (p less than 0.01) during intra-aortic balloon pumping, compared to the values before pumping and decreased by 14.9(4.2) ml.min-1 (p less than 0.01) during aortic regurgitation, compared to the values before aortic regurgitation. The coronary reserve, expressed as the ratio of the hyperaemic to the resting flow, increased by 0.7(0.1) (p less than 0.001) during intra-aortic balloon pumping and decreased by 0.4(0.2) (p less than 0.05) during aortic regurgitation. A positive significant correlation coefficient was found at the peak hyperaemic response between the mean aortic pressure and the total forward effective coronary flow, and between the mean diastolic aortic pressure and the diastolic component of the coronary flow, during both intra-aortic balloon pumping and aortic regurgitation. CONCLUSIONS: The results suggest that coronary reserve increases during intra-aortic balloon pumping and decreases during aortic regurgitation; these changes could be attributed to the effect of the pressure changes on the hyperaemic flow.

Intraventricular pumping at the mitral ring in mitral regurgitation.

This study aims at evaluating the effect of a small spherical balloon functioning during acute mitral regurgitation. Acute mitral regurgitation was produced in 11 mongrel dogs with a specially designed curved blade introduced through the left ventricular apex. Left atrial pressure, electrocardiogram, left ventricular pressure (in 8 dogs) and aortic flow (in 7 dogs) were monitored. The mean left atrial pressure increased by 9.45 +/- 2.44 mmHg (p less than 0.01) and the v wave by 14.09 +/- 2.94 mmHg (p less than 0.001). The systolic left ventricular pressure and the aortic flow decreased. The heart remained in sinus rhythm & the rate did not change significantly. After the production of mitral regurgitation, a small spherical balloon (9 to 16 cc capacity) mounted on a catheter was introduced to the left ventricle through the apex and positioned in the mitral ring. The balloon was inflated by means of a pump during systole and deflated during diastole. During its function the mean left atrial pressure decreased by 4.37 +/- 0.84 mmHg (p less than 0.001) and the v wave by 8.64 +/- 1.23 mm Hg (p less than 0.001). The systolic left ventricular pressure and the aortic flow increased. The peak systolic gradient across the mitral valve increased by 20.5 +/- 3.86 mmHg (p less than 0.01). The heart rate did not change. It is suggested that in acute mitral regurgitation the function of a small balloon could improve the hemodynamic condition by acting as a valve at the mitral ring for reduction of regurgitation and possibly by improving systolic function in severe heart failure.

Effect of the positioning of a balloon valve in the aorta on coronary flow during aortic regurgitation.

The coronary artery flow changes relative to the function of a catheter-mounted balloon valve used for relief of aortic regurgitation were studied in 10 mongrel dogs. Acute aortic regurgitation was produced by severing the aortic cusps with a long needle. Coronary flow was recorded from the left anterior descending coronary artery through an electromagnetic flowmeter. When the balloon was functioning within the cavity of the left ventricle there were no significant changes in the coronary flow and aortic pressure, except for a slight decrease in the aortic end-diastolic pressure. When it was functioning in the aortic ring the coronary flow increased 6.52 +/- 1.65 ml/min/100 gm of myocardium (p less than 0.001) and became predominantly diastolic. When it was functioning in the ascending aorta the coronary flow decreased 6.22 +/- 1.16 ml/min/100 gm of myocardium (p less than 0.001) and remained predominantly systolic. Finally, when the balloon was functioning in the thoracic aorta the coronary flow did not change significantly. With the balloon functioning in the aortic ring, ascending aorta, or thoracic aorta, there was a significant increase in the aortic end-diastolic pressure and decrease in the pulse pressure distal to the location of the balloon. It is concluded that the location of the balloon valve inserted for relief of aortic regurgitation influences the effect on coronary arterial flow.

The use of a small intra-aortic balloon to increase coronary flow.

A small spherical balloon, mounted on a catheter, was positioned, via an arteriotomy, in the ascending aorta 1 cm above the aortic valve in 10 dogs. The balloon was inflated for 60 ms, through the equipment of the intra-aortic balloon pump, during various parts of the cardiac cycle. When the inflation occurred during the rapid ejection phase, the systolic component of the coronary flow increased by 32.57 +/- 5.4 per cent (P less than 0.001), resulting in a 6.69 +/- 1.14 per cent (P less than 0.001) increase of the total (effective forward) flow. The tension time index increased by 9.01 +/- 0.85 per cent (P less than 0.001). The left ventricular end-diastolic pressure and indexes of contractility did not change. When the inflation occurred during the reduced ejection phase the increase in coronary flow and tension time index was less. When the inflation occurred during the first third of diastole, there were no significant changes in the pressures and flow. In the middle third of diastole, the inflation of the balloon produced a 6.5 +/- 0.99 per cent (P less than 0.001) increase of the total flow, without significant changes in the pressures, except for a small increase in the mean diastolic aortic pressure. When the inflation occurred in the last third of diastole, the total coronary flow increased by 10.47 +/- 1.06 per cent (P less than 0.001). There was a decrease in the aortic end diastolic pressure and a 1.08 +/- 0.42 per cent (P less than 0.02) increase in the time tension index. In five dogs, additional observations were made using another mode of inflation. The balloon remained inflated during the entire diastolic period. The total coronary flow increased by 17.46 +/- 4.8 per cent (P less than 0.01), along with a small increase in the diastolic aortic pressure. Indexes of contractility did not change. In conclusion, a small spherical balloon functioning as a pump in the ascending aorta, in close proximity to the coronary ostia, can significantly increase the coronary blood flow.

Intra-aortic ballon pump for relief of aortic regurgitation. Experimental study.

Backflow from the aorta to the left ventricle during diastole in aortic regurgitation can be reduced by expanding, during diastole, a small air balloon positioned in the ascending aorta downstream to the regurgitant valve. A spherical catheter-mounted balloon, acting as a prosthetic aortic valve for the correction of acute aortic regurgitation, was tested in 12 dogs. This "valve" was actively inflated and deflated by means of a common intra-aortic balloon pumping system (Datascope). A significant increase of end-diastolic pressure in the descending aorta, from 51.72 +/- 1.72 to 70.35 +/- 1.92 mm Hg (mean +/- standard error, p less than 0.001), was obtained, without a significant pressure gradient across the "valve". The "valve" prevented the backward flow of the descending aorta by up to 100%, so that there was a mean increase in t-e effective forward flow of 12.61 +/- 5.27% (mean +/- standard error, p less than 0.05). Coronary arterial flow changes varied during the application of the "valve." They depended directly on the changes of the diastolic component of the flow velocity wave, and this relationship was significant (x2 = 33.04, p less than 0.0001). Contractility indices were not significantly affected during the function of the "valve." It is suggested that the spherical "valve" mounted on a catheter may easily be inserted without thoracotomy for a temporary satisfactory correction of the aortic regurgitation.