Myocardial oxygen consumption is affected by dynamic cardiomyoplasty in dogs with adriamycin-induced cardiomyopathy

The surgical treatment of heart failure. A new frontier: nontransplant surgical alternatives in heart failure

Heart failure may affect 500,000 new people each year. Heart transplantation has leveled off at approximately 2,500-3,000 cases per year in the United States. Thus, new nontransplant surgical alternatives may be necessary to treat many of the patients who progress to intractable Class III, or especially Class IV heart failure. In addition to left ventricular assist devices, other operations have been used and are now being developed for this purpose. These include left ventricular resection (Batista operation), mitral valve repair, autologous skeletal muscle cardiac assist, splint and compression devices, as well as left ventricular reconstruction by the Dor procedure. All of these procedures have been, and are currently being, evaluated for the surgical treatment of congestive heart failure and they will be reviewed in this article. Although many appear very promising, ongoing trials and retrospective reviews will be increasingly necessary to vigorously define which of the nontransplant surgical alternatives are the best procedures going forward for the large numbers of patients with congestive failure.

Cardiomyoplasty reduces myocardial oxygen consumption: implications for direct mechanical compression

BACKGROUND

This study investigates the possibility of reducing myocardial oxygen consumption by dynamic cardiomyoplasty in chronic heart failure. The sheep model used is relevant for cardiac assist using direct mechanical cardiac compression.

METHODS

In 7 sheep, heart failure was induced by staged intracoronary microembolization followed by dynamic cardiomyoplasty. Six months later, the effect of latissimus dorsi muscle stimulation in the 2:1 mode (on, cardiomyoplasty; off, control) was studied. Left ventricular pressure-volume loops were obtained by conductance, micromanometer, and inferior vena cava occlusion catheter. Myocardial oxygen consumption was derived from left main coronary artery blood flow and oxygen content of arterial and coronary sinus blood.

RESULTS

Cardiomyoplasty had no significant effect on left ventricular hemodynamic variables such as end-systolic pressure. However, cardiomyoplasty increased stroke volume and ejection fraction significantly by 11% +/- 12% and 11% +/- 10%, respectively. Although pressure-volume area and external work did not increase with cardiomyoplasty, myocardial oxygen consumption decreased by 21% +/- 11%. Therefore, cardiomyoplasty increased myocardial efficiency (external work/myocardial oxygen consumption) by 16% +/- 13%.

CONCLUSIONS

Despite limited hemodynamic improvement from dynamic cardiac compression by cardiomyoplasty in sheep with chronic heart failure, myocardial oxygen consumption was significantly reduced. These findings provide a rationale for reverse remodeling of the failing heart using direct mechanical compression.

Adriamycin-induced cardiomyopathy in the dog--an appropriate model for research on partial left ventriculectomy?

OBJECTIVE

To evaluate the adriamycin-induced cardiomyopathy in the dog for research on partial left ventriculectomy (PLV).

METHODS

An intracoronary catheter was introduced into the left main stem via the first diagonal branch in a retrograde fashion in 6 adult FBI (Foxhound Boehringer Ingelheim) dogs weighing 30 to 35 kg. The catheter was connected to a percutaneous access port that was used for weekly adriamycin administration (10 mg over a 1-hour period for 5 times). Follow-up examinations (transthoracic echocardiography, hemodynamic parameters, cardiopulmonary status, and neurohormones) were done before, 1 week after the last adriamycin administration, and 6 weeks later. After the last measurements, all dogs were euthanized with saturated potassium chloride under general anesthesia and the hearts were excised for histologic examinations. All data were calculated as mean values and standard error of the mean. Differences were calculated by the Wilcoxon signed rank test for paired and unpaired data. p values less than 0.05 were considered significant.

RESULTS

Central venous pressure (2.2 +/- 0.8 vs 5.2 +/- 0.4 mm Hg, p = 0.03), mean pulmonary artery pressure (8.6 +/- 1.1 vs 12.4 +/- 0.5 mm Hg, p = 0.03), pulmonary wedge pressure (2.6 +/- 0.9 vs 7.0 +/- 0 mm Hg, p = 0.03), left ventricular endsystolic diameter (2.5 +/- 0.2 vs 3.1 +/- 0.4 cm, p = 0.03), and enddiastolic (4.5 +/- 0.2 vs 4.9 +/- 0.2 cm, p = 0.03) diameter increased significantly after adriamycin administration, whereas cardiac output (4.0 +/- 0.3 vs 3.3 +/- 0.1 liter/min, p = 0.03), stroke volume index (66.0 +/- 7.4 vs 54.0 +/- 3.9 ml/beat/m(2), p = 0.03), and ejection fraction (61.1 +/- 5.1 vs 37.7 +/- 5.7%, p = 0.03) decreased markedly. These changes were accompanied by a significant decline of oxygen delivery (1130 +/- 170 vs 790 +/- 65 ml/min, p = 0.03), which led to an enhanced oxygen extraction (0.12 +/- 0.01 vs 0.24 +/- 0.01, p = 0.03). Consequently, venous oxygen saturation (82.7 +/- 4.1 vs 71.3 +/- 2.5%, p = 0.03) decreased. Troponin I (0.02 +/- 0.025 vs 1.7 +/- 0.6 ng/ml, p = 0.03) and the anti-diuretic hormone (1.9 +/- 0.9 vs 20.0 +/- 1.9 pg/ml, p = 0.03) increased significantly after adriamycin administration. Deterioration of cardiac function continued after termination of adriamycin administration, albeit slower than during adriamycin administration. All hearts had severe histologic alterations, which were characteristic of adriamycin-induced toxicity: cytoplasmic vacuolation, myocyte degeneration, and increased fibrosis.

CONCLUSIONS

The adriamycin-induced cardiomyopathy in the dog is similar to the dilated cardiomyopathy in humans and may be an appropriate model for PLV.

Adynamic cardiomyoplasty: effect on cardiac efficiency and contractile reserve in dogs with adriamycin-induced cardiomyopathy

The girdling effect of the skeletal muscle wrap seems to be the primary mechanism of action of cardiomyoplasty. It is associated with a myocardial sparing effect. Myocardial sparing effect has been shown with an active muscle wrap or an active muscle wrap acutely turned "OFF". The purpose of the study was to evaluate the effect of a passive skeletal muscle wrap on cardiac energetics parameters and contractile reserve in a canine model of cardiomyopathy. Six dogs with adriamycin-induced cardiomyopathy were studied. Three dogs underwent right latissimus dorsi adynamic cardiomyoplasty and 3 served as controls. Cardiac and coronary sinus catheterizations were performed at 0 and 6 weeks. A dobutamine stress test was performed at 6 weeks. Myocardial oxygen consumption was not reduced in the cardiomyoplasty group (139.20+/-86.90 Joules/min) compared to the control group (95.10+/-12.60 Joules/min, P = 0.27) at 6 weeks. Mechanical cardiac efficiency was increased in the cardiomyoplasty group (33.15+/-4.40%) compared to the control group (24.50+/-2.70%, P = 0.049) at 6 weeks. Left ventricular end diastolic diameter index was reduced in the cardiomyoplasty group (38.00+/-1.70 mm/m2) compared to the control group (46.30+/-1.55 mm/m2, P = 0.049) at 6 weeks. Indices of diastolic function -dp/dt, and tau were not significantly affected by adynamic cardiomyoplasty. Max dp/dt was increasing more in the cardiomyoplasty group than in the control group (P = 0.07) during dobutamine stress test. Mechanical cardiac efficiency was better preserved by the adynamic cardiomyoplasty. Myocardial contractile reserve might be better preserved with cardiomyoplasty.

Hypervolaemia improves global and local function and efficiency in postischaemic myocardium

1. In the present study, we investigated the effects of blood volume on postischaemic function and efficiency. In 14 anaesthetized dogs, following recovery from a period of 15 min occlusion of the left anterior descending coronary artery, the effects of hypervolaemia (HYPER; 15% increased volume produced by fast infusion of Hespan; B Braun Medical, Irvine, CA, USA), normovolaemia (NORMO) and hypovolaemia (HYPO) were studied. 2. Although myocardial O2 consumption was not significantly increased by volume (6.37+/-0.94 vs 6.89+/-1.1 mL/min per 100 g for HYPO and HYPER, respectively), local work of the stunned myocardium was markedly elevated (8.8+/-1.7 vs 22.5+/-3.5 g.mm/ beat, for HYPO and HYPER, respectively; P < 0.05). External work of the heart was also significantly improved (71.8+/-12.7 vs 139.5+/-16.2 mmHg.L/min for HYPO and HYPER, respectively). These data indicate markedly improved efficiency produced by volume, because work was increased with no change in myocardial O2 consumption. 3. Local dysfunction was characterized by several parameters, including systolic bulge, end-diastolic length, delay to onset of shortening, end shortening time delay (EST) and tail work ratio. Hypervolaemia reduced EST compared with hypovolaemia (98.6+/-18.3 vs 110.7+/-14.9 msec, respectively; P < 0.05) and improved tail work ratio (28.0+/-7.0 vs 36.0+/-7.0%, respectively; P < 0.05), with no effects on systolic bulge, end-diastolic length and delay to onset of shortening. 4. Thus, even in the postischaemic myocardium, increasing work by volume is energetically efficient and is accompanied by partial improvement of local dysfunction.