Osamu Kawaguchi

Dynamic cardiac compression improves contractile efficiency of the heart

The effect of dynamic cardiac compression on left ventricular contractile efficiency was assessed in terms of the pressure-volume relationship and myocardial oxygen consumption. In 11 excised cross-circulated dog hearts, the ventricle was directly compressed during systole (dynamic cardiac compression). Measurements for pressure-volume area (a measure of total mechanical energy), external work, and myocardial oxygen consumption were done before and during dynamic cardiac compression. Dynamic cardiac compression increased pressure-volume area by 28% +/- 17% (mean plus or minus the standard deviation) and external work by 24% +/- 20% (p = 0.0000185 and 0.0000212, respectively) at given end-diastolic and stroke volumes without affecting myocardial oxygen consumption. As a result, the oxygen cost of pressure-volume area, that is, the slope of the myocardial oxygen consumption-pressure-volume area relationship, significantly decreased by 16% +/- 13% (p = 0.0000135) whereas the pressure-volume area-independent myocardial oxygen consumption was unchanged. Then, contractile efficiency, that is, the reciprocal of the slope of the myocardial oxygen consumption-pressure-volume area relationship in joules significantly improved from 45% +/- 8% to 53% +/- 13% (p = 0.0000437). When the native myocardial oxygen consumption-pressure-volume area relationship was assessed by subtracting the dynamic cardiac compression pressure applied to the heart, the slope of the myocardial oxygen comsumption-pressure-volume area relationship returned to the control level. This indicates that the contractile efficiency of the native heart was not affected by dynamic cardiac compression. We conclude that dynamic cardiac compression enhances left ventricular pump function by improving the contractile efficiency of the overall heart leaving the energetics of the native heart unchanged.

A stable ovine congestive heart failure model. A suitable substrate for left ventricular assist device assessment.

Similarities in coronary circulation and heart size of sheep to that of humans are specific advantages of a sheep model of congestive heart failure (CHF). CHF was created in 11 sheep (51 ± 4 kg) by selective sequential intracoronary injection of 90 μ microspheres under 1.5% isoflurane anesthesia. Hemodynamic characteristies were assessed at baseline, 4 weeks after establishment of CHF (ejection fraction [EF] < 35%, n = 11), and 26 weeks (n = 7) later. Baseline echocardiographic EF was 59 ± 5% and fell to 26 ± 5% after 5 ± 2 embolizations. The left ventricular (LV) pressure-volume relationship showed stable decreases in LV end-systolic elastance (Ees) and preload recruitable stroke work. Intravenous infusion of dobutamine increased Ees from 2.8 ± 1.7 to 4.3 ± 2.2 and 4.5 ± 1.4 mmHg/ml at heart rates of 140 and 160/min, respectively, at baseline. Increases of Ees (from 1.3. ± 0.5 to 2.3 ± 0.7 and 1.9 ± 0.5 mmHg/ml at heart rates of 140 and 160/min, respectively) with dobutamine under CHF conditions did not exceed Ees values at baseline without dobutamine. This response to dobutamine infusion did not change 26 weeks after establishment of CHF. This stable ovine CHF model is proposed for studies on the long-term effects of cardiac assist devices. ASAIO Journal 1997; 43:M408-M413.

Ventriculoarterial coupling with intra-aortic balloon pump in acute ischemic heart failure

PURPOSE We analyzed the mechanism of effects of intra-aortic balloon pumping using the pressure-volume relationship and ventriculoarterial coupling in the normal and failing hearts. MATERIALS In 12 anesthetized Holstein calves (weight, 94 +/- 8 kg), the ventricular end-systolic and arterial elastances, pressure-volume area, and external work were analyzed during steady-state contractions with traditional hemodynamic parameters with intra-aortic balloon pumping-off and -on (1:1 synchronous ratio). An acute ischemic heart failure was induced by injecting 10 microm microspheres (4.2 +/- 1.8 x 10(7). 100g left ventricular weight-1) into the left main coronary artery; all measurements were repeated. RESULTS Intra-aortic balloon pumping did not change hemodynamic parameters in the control. However, during heart failure, intra-aortic balloon pumping decreased the arterial elastance from 3.6 +/- 1.3 mm Hg to 2.9 +/- 1.2 mm Hg. mL-1 while not affecting the ventricular end-systolic elastance, this resulted in an improvement of the ventriculoarterial coupling ratio from 3.1 +/- 0.8 to 2.3 +/- 0.8. Intra-aortic balloon pumping decreased not only end-systolic pressure (from 69 +/- 16 mm Hg to 64 +/- 19 mm Hg) but end-diastolic volume and pressure (from 139 +/- 38 mL to 137 +/- 37 mL and from 13. 9 mm Hg to 12.8 mm Hg, respectively) with the leftward shift of the pressure-volume loop. Pressure-volume area decreased (from 914 +/- 284 mm Hg to 849 +/- 278 mm Hg. mL) although stroke volume increased (from 21 +/- 6 mL to 24 +/- 6 mL). CONCLUSION Reduction of the arterial elastance with intra-aortic balloon pumping improved the ventriculoarterial coupling ratio and increased stroke volume. Leftward shift of the pressure-volume loop resulted in the reduction of pressure-volume area, which suggests the conservation of the myocardial oxygen consumption.

In vivo testing of a completely implanted total artificial heart system.

The authors performed 14 implants of a completely implanted total artificial heart (TAH) system in calves. The system consisted of a dual pusher plate rollerscrew energy converter, two sac type blood pumps, an implanted electronic control and battery package, and a transcutaneous energy transmission system. Ten of the implants included a percutaneous lead for monitoring of the implant; the remainder made use of wireless two way telemetry between the implant and the outside. Three animals survived the perioperative period. These calves survived for 98 to 118 days, and one was still alive at 150 days. Causes for termination of the 98 and 118 day cases were abdominal pocket sepsis originating at a monitoring line, and systemic sepsis acquired perioperatively. Death or termination in the shorter cases was mainly due to respiratory complications or bleeding. The TAH system proved capable of providing adequate cardiac outputs at modest atrial pressures. Wireless monitoring and wireless intervention for weaning from cardiopulmonary bypass were readily achieved. All organ systems functioned normally in the presence of the device. Once recovery from implantation in these very young animals was achieved, the system proved its ability to reliably support these animals until body mass exceeded its cardiac output capabilities.

Left ventricular mechanoenergetics during asynchronous left atrial–to–aortic bypass: Effects of pumping rate on cardiac workload and myocardial oxygen consumption

The purpose of this study was to analyze left ventricular energetics during asynchronous, pulsatile left atrial to aortic bypass in the failing heart with the use of the pressure-volume relationship. In 12 anesthetized Holstein calves (body weight 94 +/- 7 kg), 10 microns microspheres (3.3 x 10(7) +/- 1.1 x 10(7)/100 gm left ventricular weight) were injected into the left main coronary artery to induce heart failure. Baseline left ventricular end-systolic elastance significantly decreased from 7.9 +/- 0.7 to 5.5 +/- 0.4 mm Hg/ml 100 gm left ventricular weight. Left ventricular pressure was measured with a micromanometer, and ultrasonic dimension transducers measured left ventricular orthogonal diameters. Ellipsoidal geometry was used to calculate simultaneous left ventricular volume. End-systolic elastance, pressure-volume area, external work, potential energy, and myocardial oxygen consumption were analyzed during steady-state contractions. After pre-pulsatile left atrial to aortic bypass measurements were taken, the measurements were repeated during asynchronous pulsatile left atrial to aortic bypass at the maximal pumping rate (69 +/- 13 beats/min) termed 100%, and then 80%, 60%, and 40% of the maximal pumping rate in the full to empty mode. With increases in pumping rate, pressure-volume area and external work proportionally decreased, whereas potential energy remained unchanged except for 100% of maximal pumping rate. Pressure-volume area correlated linearly with myocardial oxygen consumption during asynchronous pulsatile left atrial to aortic bypass (r = 0.971). As a result, pumping rate correlated linearly with conservation of myocardial oxygen consumption (r = 0.998). In conclusion, decreased pressure-volume area accounts for the reduction in myocardial oxygen consumption during asynchronous pulsatile left atrial to aortic bypass. Conservation of myocardial oxygen consumption is mainly attributed to the reduction of external work.

A completely implanted left ventricular assist device : chronic in vivo testing

A completely implantable left ventricular assist device (LVAD) designed for permanent circulatory support has recently been tested in animals without the use of percutaneous leads, using transcutaneous energy transmission and wireless telemetry. The LVAD consists of a brushless DC motor and rollerscrew energy converter, a pusher plate actuated blood pump with a seamless segmented polyurethane blood sac, Bjork-Shiley Delrin disk monostrut valves, an implanted compliance chamber, an implanted electronic controller and battery, and a transcutaneous energy transmission system. The blood pump/energy converter assembly weighs 565 g and displaces 295 cc. The dynamic stroke volume is 60 ml, and the maximum output is 9 L/min. Pump output is automatically controlled to maintain full stroke volume as preload varies. Hall effect sensors for detecting rotary position of the motor are the only sensors used. Six bovine implants were performed, with durations of 84, 208, 244, 130, 70 (ongoing), and 15 (ongoing) days. Four animals used two-way telemetry, whereas the remaining two used one-way (outgoing) telemetry. These first chronic in vivo tests with the Penn State completely implanted LVAD system have demonstrated that it is a feasible solution to long-term ventricular support.

Left ventricular mechanics during synchronous left atrial-aortic bypass

The purpose of this study was to analyze left ventricular mechanics during asynchronous, pulsatile left atrial-aortic bypass before and after microsphere injection with the pressure-volume relationship. In 14 anesthetized Holstein calves, left ventricular pressure was measured with a micromanometer and ultrasonic dimension transducers measured left ventricular orthogonal diameters. Ellipsoidal geometry was used to calculate simultaneous left ventricular volume. Contractility index, pressure-volume area, external work, and potential energy were calculated during steady-state contractions. These measurements were repeated during pulsatile left atrial-aortic bypass. To induce heart failure, we injected microspheres into the left main coronary artery, and the protocol for baseline and pulsatile left atrial-aortic bypass was repeated. Despite the significant differences in the baseline contractility index (7.4 +/- 0.7 mm Hg/ml versus 4.7 +/- 0.5 mm Hg/ml), contractility index remained the same during pulsatile left atrial-aortic bypass in control and heart failure modes, respectively. Pulsatile left atrial-aortic bypass significantly decreased end-diastolic volume (22% and 17%), pressure-volume area (58% and 48%) and external work (74% and 69%, all p < 0.05) during control and heart failure measurements, respectively. However, it did not change end-systolic volume or potential energy. In conclusion, asynchronous pulsatile left atrial-aortic bypass did not affect left ventricular contractile state in either the normal or failing heart. Although decreased pressure-volume area accounts for the reduction in myocardial oxygen consumption, unchanged potential energy suggested a limited unloading of the ventricle.

Clinical Characteristics of Bicuspid Aortic Valves in Surgical Patients

Of 413 patients undergoing surgery for aortic valve disease, 42 were confirmed to have congenital bicuspid aortic valve. There were 24 males and 18 females, with a mean age of 54.9 ± 14.6 years. The etiology of the surgical indications in patients with bicuspid valves were degeneration, rheumatic disease, and infectious endocarditis. Thirty-two patients had aortic stenosis and 10 had aortic regurgitation. Infective endocarditis was seen mainly in patients ≤50 years of age at the time of surgery, while degenerative aortic stenosis occurred more often in older patients. The annular diameter measured during surgery was significantly narrower in the 42 patients with bicuspid valves compared to 371 patients with tricuspid valves who underwent aortic valve replacement during the same period. It is important to prevent infectious endocarditis in younger patients diagnosed with bicuspid aortic valve, whereas careful attention should be paid to decalcification during surgery in older patients because the vast majority suffer from degenerative aortic stenosis.

Thoracoscopic approach for biopsy of the latissimus dorsi cardiomyoplasty wrap

J Thorac Cardiovasc Surg Carrington, Christopher Horam, Peter Brady and Stephen N. Hunyor Melissa A. Bochner, Regina Crameri, Yi Fei Huang, Osamu Kawaguchi, Russell Thoracoscopic approach for biopsy of the latissimus dorsi cardiomyoplasty wrap http://jtcs.ctsnetjournals.org/cgi/content/full/115/4/958 the World Wide Web at: The online version of this article, along with updated information and services, is located on

Linear end-systolic pressure-volume relationship during pulsatile left ventricular bypass represents native heart function ☆ ☆☆ ★ ★★ ♢

This study assessed whether the end-systolic pressure-volume relationship obtained without any interventions during pulsatile left ventricular bypass adequately represents native heart function. In 11 anesthetized Holstein calves, left ventricular pressure was measured with a micromanometer while left ventricular volume was simultaneously calculated from orthogonal left ventricular diameters measured with ultrasonic dimension transducers. End-systolic pressure and volume data were subjected to linear regression analysis to achieve an end-systolic pressure-volume relationship. Data from both caval occlusions and aortic occlusion were used for the control end-systolic pressure-volume relationship (median r = 0.941, slope = 7.4 +/- 0.8 mm Hg per milliliter per 100 gm left ventricular weight; mean +/- standard error of the mean). During left atrial-aortic bypass with a Pierce-Donachy pneumatic assist pump in the asynchronous mode, the end-systolic pressure-volume relationships were obtained without interventions to change ventricular loading conditions. During maximal ventricular unloading during full to empty pumping, termed 100%, the resulting narrow range of pressure and volume data did not yield highly linear end-systolic pressure-volume relationships (median r = 0.669, slope = 4.9 +/- 0.9 mm Hg per milliliter per 100 gm left ventricular weight). However, at reduced rates off pumping, the end-systolic pressure-volume relationships were considerably linear (80%, median r = 0.819; 60%, median r = 0.868; 40%, median r = 0.899). Slopes did not significantly differ from control values (80%, 6.9 +/- 1.1; 60%, 8.2 +/- 1.1; 40%, 7.8 +/- 1.1). The end-systolic pressure-volume relationship obtained without exogenous load changes during asynchronous, pulsatile left ventricular bypass represents native left ventricular systolic function.