Right latissimus dorsi cardiomyoplasty for left ventricular failure.

Recent experimental studies have shown that cardiomyoplasty using the right latissimus dorsi provides excellent hemodynamic augmentation. Based on these experimental findings, this procedure was performed in a 40-year-old man with a dilated cardiomyopathy after a large myocardial infarction. The patient tolerated the procedure well and has had marked functional improvement. Examination 6 months after operation demonstrated decreases in right atrial pressure, pulmonary capillary wedge pressure, and left ventricular end-diastolic volume. In addition, increases were noted in cardiac output, stroke volume, left ventricular stroke-work, right ventricular ejection fraction, and left ventricular ejection fraction. Because of this promising clinical result, we have started a series of right latissimus dorsi cardiomyoplasties for left ventricular failure.     

Update 2001: Right latissimus dorsi cardiomyoplasty augments left ventricular systolic performance

As Originally Published in 1993: Right Latissimus Dorsi Cardiomyoplasty Augments Left Ventricular Systolic Performance by Stephen E. Park, MD, Brian L. Cmolik, MD, Robert R. Lazzara, MD, Dennis R. Trumble, MS, and James A. Magovern, MD. Department of Surgery, Allegheny General Hospital, Surgical Research, Allegheny-Singer Research Institute, and Allegheny Campus, The Medical College of Pennsylvania, Pittsburgh, Pennsylvania, USA

We hypothesized that the right latissimus dorsi cardiomyoplasty augments left ventricular performance. Five dogs underwent staged right latissimus dorsi cardiomyoplasty. Ventricular function was studied 1 to 3 weeks later. Left ventricular pressure was measured with a micromanometer and left ventricular dimensions with piezoelectric crystals. Inferior vena caval occlusion was used to vary preload. Pressure-volume data were collected with the muscle unstimulated and stimulated at 1:2 and 1:1 muscle/heart ratios. The end-systolic pressure-volume relation (mm Hg/mL), stroke work, preload recruitable stroke work, left ventricular end-diastolic volume, and the diastolic relaxation constant were calculated and expressed as mean ± standard deviation. Stimulated beats at a 1:2 ratio showed an increase in stroke work of 42.1% (978 ± 381 to 1,390 ± 449 g · cm; p < 0.01) and preload recruitable stroke work of 28.8% (59.4 ± 20.7 to 76.6 ± 11.0 g · cm/cm³; p = 0.05) compared with the unstimulated beats. With the stimulator on at 1:1, smaller changes occurred: stroke work increased 9% (1,167 ± 390 to 1,273 ± 363 g · cm; not significant) and preload recruitable stroke work increased 27% (63.9 ± 22.7 to 80.9 ± 23.1 g · cm/cm³; p = 0.05). There were no significant changes in the end-systolic pressure-volume relation. The diastolic relaxation constant did not change at 1:1 (36 ± 9.7 to 37 ± 6.4 ms; not significant) or 1:2 (36 ± 9.3 to 39 ± 8.2 ms; not significant). Left ventricular end-diastolic volume was unchanged at 1:1 (34 ± 10.7 to 32 ± 10.3 mL) and at 1:2 (31 ± 9.0 to 32 ± 8.7 mL). Right unconditioned latissimus dorsi cardiomyoplasty in anesthetized dogs with normal hearts resulted in enhanced systolic work and contractility with no change in diastolic relaxation at stimulation rates of 1:2 and 1:1.     

Bilateral latissimus dorsi cardiomyoplasty.

This study was undertaken to test the hypothesis that a bilateral latissimus dorsi cardiomyoplasty provides greater hemodynamic augmentation than a unilateral procedure. Two types of bilateral procedure and a left posterior cardiomyoplasty were tested in each of 8 mongrel dogs. R-wave synchronous muscle pacing was achieved with a programmable burst stimulator. Hemodynamic variables of stimulated beats were compared with those of a nonstimulated baseline using paired t tests. The effects of a double anterior muscle wrap were equal to a right anterior/left posterior configuration. Therefore, the data on the two types of bilateral procedure were combined and compared with the left wrap. Stimulation of the bilateral cardiomyoplasty resulted in significant increases in right ventricular pressure (44 +/- 3.1 versus 26 +/- 1.8), first derivative of right ventricular pressure (595 +/- 117 versus 196 +/- 14), pulmonary artery pressure (34 +/- 1.9 versus 23 +/- 1.6), left ventricular pressure (90 +/- 5.9 versus 69 +/- 5.3), first derivative of left ventricular pressure (1454 +/- 141 versus 1072 +/- 107), aortic pressure (80 +/- 5.4 versus 67 +/- 4.9), and peak aortic flow (9.4 +/- 1.1 versus 7.7 +/- 0.8) (p less than 0.05). Significant increases in all of these variables also occurred with stimulation of the left cardiomyoplasty, but the increases in right ventricular pressure, first derivative of right ventricular pressure, pulmonary artery pressure, and aortic pressure were larger for the bilateral than the left cardiomyoplasty. The bilateral and the left procedure can each augment systolic ventricular function. The bilateral procedure appears to have greater effects, especially on right ventricular function.     

Growth potential of latissimus dorsi muscle flaps used in the cardiomyoplasty procedure

Synchronously stimulated latissimus dorsi muscles have been used for cardiomyoplasty in adult patients with heart failure. This procedure has the potential of being used in pediatric patients to enlarge a hypoplastic ventricle or to reinforce the right atrium in the Fontan procedure. The growth potential of such a myograft was studied. Young piglets weighing 18 to 22 kg underwent right latissimus dorsi cardiomyoplasty while the latissimus dorsi weight and myoplasty area were measured. In half of the animals, the myograft was not stimulated and in the others it was continuously stimulated with an atrioventricular sequential pacemaker to contract in synchrony with the heart. Two months later, with doubling of body weight, the hearts were removed for study. In both groups, significant (p less than 0.05) increase in latissimus dorsi weight (+92% +/- 15% nonpaced versus +77% +/- 3% paced) and myoplasty area (+107% +/- 13% nonpaced versus +116% +/- 30% paced) were noted. The results in stimulated versus nonstimulated animals were not significantly different. Thus, not only does cardiomyoplasty offer a contractile tissue to repair or enlarge cardiac chambers, but this tissue can also grow in young patients and avoid subsequent size mismatch.     

Latissimus dorsi dynamic cardiomyoplasty

Cardiomyoplasty is a new surgical technique that uses an electrostimulated skeletal muscle to reinforce or partially replace the heart muscle. Since the first clinical case performed in 1985, long-term beneficial cardiac effects of latissimus dorsi cardiomyoplasty have been documented in patients with various myocardial diseases (ischemic, neoplastic, dilated cardiomyopathy). In this article we describe the surgical technique that we have developed to biomechanically assist severe and irreversible ventricular failure.     

Demand dynamic cardiomyoplasty: mechanograms prove incomplete transformation of the rested latissimus dorsi

BACKGROUND: In dynamic cardiomyoplasty, standard stimulation produces high fatigue resistance but also undesirable dynamic characteristics of the latissimus dorsi (LD). Based on results of intermittent stimulation in animals we introduced demand stimulation, a lighter regimen of LD activity-rest stimulation, and the mechanogram, a noninvasive method to determine the contractile characteristics of LD wrap. METHODS: Surgery and standard stimulation was according to the technique of Carpentier and Chachques, demand stimulation and LD wrap mechanogram were as we previously described. The LD contraction is synchronized to heart systole by mechanogram and echocardiography, and extent of transformation by tetanic fusion frequency analysis. A total of 22 patients were studied to date. Data for the 8 subjects who attained 6-month follow-up are reported. Four of them were lightly stimulated from the conditioning period, whereas 4 others were converted to light and then demand stimulation after years of standard stimulation. Patients were followed up with respect to survival, functional class, hospital admission rate, medication used, cardiopulmonary exercise testing, and LD wrap mechanography. RESULTS: Latissimus dorsi wrap slowness reverses by the activity-rest regimen, even after years of standard stimulation (Tetanic fusion frequency of 11 +/- 2 Hz after standard stimulation vs 30 +/- 3 Hz after demand regimen, p < 0.0001). After demand dynamic cardiomyoplasty there are no deaths. Quality of life is substantially improved with significant reduction of heart failure symptoms (New York Heart Association class: preoperative 3.0 +/- 0.0, post-demand dynamic cardiomyoplasty 1.5 +/- 0.2, p < 0.0001). In the subgroup of patients lightly stimulated from LD conditioning, exercise capacity tends to increase over preoperative values more than 2 years after operation (VO2 max: preoperative 12.3 +/- 0.7 vs 16.6 +/- 1.7 post-demand dynamic cardiomyoplasty, p = 0.05). CONCLUSIONS: Demand stimulation and mechanography of the LD wrap are safe procedures that could offer long-term benefits of dynamic cardiomyoplasty to patients with pharmacologically intractable heart failure.     

Full-thickness dynamic cardiomyoplasty of the left ventricle with free revascularized latissimus dorsi myografts. An experimental feasibility study.

Dynamic cardiomyoplasty, with use of a free latissimus dorsi myograft revascularized by the internal thoracic artery and vein, was performed in eight dogs subjected to electrical preconditioning for 8 to 12 weeks (group I) and in six unconditioned dogs (group II). The procedure was performed after the resection of the anterior wall of the left ventricle. Cardiac output and left ventricular stroke work were augmented by 23.7% +/- 9.4% and 44.1% +/- 15.9% after graft pacing with 50 Hz burst stimulation at a 1:1 synchronization ratio, while left atrial pressure ranged from 8 to 12 mm Hg. Analysis of the left ventricular function curve showed that graft pacing at rates of 1:1, 2:1, and 3:1 augmented global left ventricular function. Hemodynamic benefit by continuous pacing at a 3:1 ratio was seen for 1.97 +/- 1.90 hours (0.5 to 6.1 hours) in group I until complications unrelated to the graft terminated the study, while it lasted for only 0.19 +/- 0.09 hour in group II. During the stimulation, the ratio of the lactate output to the oxygen consumption of the graft in group I, a possible indicator of metabolic shift, was significantly less than in group II, (0.46 +/- 0.58 and 6.34 +/- 1.73; p < 0.01). We conclude that free grafts of transformed latissimus dorsi muscle can augment global left ventricular performance, with a physiologic preload by oxidative metabolism, and provide a viable option in full-thickness dynamic cardiomyoplasty.     

Diabetes-induced alterations in latissimus dorsi muscle properties impair effectiveness of dynamic cardiomyoplasty in rats

Short-term diabetes was induced in male Wistar rats with streptozotocin injection. The effects of diabetes on latissimus dorsi (LD) muscle contractile and biochemical properties and acute cardiomyoplasty (CDM) were assessed and compared with data from 16 control rats. Isometric force, contractile properties, and fatigue were measured in electrically stimulated muscles (0.3 ms, 1-256 Hz), and Na+K+ and Ca2+ATPase activities were quantified in muscle membrane preparations. Systolic arterial pressure and aortic blood flow were recorded at rest and during LD muscle stimulation. Compared with control muscle, diabetic muscle showed smaller maximum specific tetanic tension and lower rates of rise and fall in force. Diabetic LD muscle also showed lower muscle enzyme activities. Twitch tension and fatigue did not differ between groups. Smaller increases in aortic flow and systolic pressure after CDM were found in diabetic rats compared to controls. The marked decrease in CDM effectiveness in diabetic rats likely reflected the alterations in muscle properties associated with diabetes.     

Vascular delay of the latissimus dorsi provides an early hemodynamic benefit in dynamic cardiomyoplasty.

OBJECTIVES: Dynamic cardiomyoplasty (CMP) as a surgical treatment for chronic heart failure improves functional class status for most patients. However, significant hemodynamic improvement with latissimus dorsi muscle (LDM) stimulation has not been consistent. The current protocols do not allow early LDM stimulation after CMP surgery. We hypothesized that vascular delay of LDM would increase myocardial assistance after CMP and allow early (48-h) LDM stimulation after CMP. METHODS: Mongrel dogs (n = 24) were divided in four groups: 1) controls (n = 6), single-stage CMP; 2) Group ES (n = 6), single-stage CMP with early LDM stimulation beginning 48 h, postoperatively; 3) Group VD (n = 6), vascular delay of the LDM followed by CMP without early LDM stimulation, and 4) Group VDES (n = 6), vascular delay of LDM (14-18 days), followed by CMP with early stimulation (48 h postoperatively). Two weeks after CMP, global cardiac dysfunction was induced by injecting microspheres into the left coronary artery. LDM-assisted (S) beats were compared with nonstimulated beats (NS) by measuring aortic pressure (AoP), LV pressure, aortic flow, and by calculating first derivative of LV contraction (+/-dP/dt), stroke volume (SV), and stroke work (SW). RESULTS: In ES, LDM stimulation had no effect on the hemodynamic parameters. In the other groups, LDM stimulation significantly (p < 0.05) increased AoP, LVP, dP/dt, SV, and SW. However, these increases were much larger in VD and VDES. In VD, LDM stimulation increased peak AoP by 21.5+/-3.8 mm Hg, LVP by 22.1+/-4.1 mm Hg, dP/dt by 512+/-163 mm Hg/sec, SV by 10.4+/-2.3 mL, and SW by 22.1+/-5.4 g/m(-1). Similarly, in VDES, LDM stimulation increased peak AoP by 24.1+/-4.7 mm Hg, LVP by 26.2+/-4.3 mm Hg, dP/dt by 619+/-47 mm Hg/sec, SV by 6.5+/-0.7 mL, and SW by 16.7+/-4.1 g/m(-1). CONCLUSIONS: In dogs with global LV dysfunction, CMP after vascular delay resulted in a significant improvement in hemodynamic function measured 2 weeks after surgery. This improvement was not provided by single-stage CMP with or without early stimulation. Vascular delay of the LDM before surgery may play an important role for early benefit after CMP, shorten the overall muscle training period, as well as increase hemodynamic response to LDM stimulation.     

Hydraulic pouches of canine latissimus dorsi. Potential for left ventricular assistance

We have studied the fatigue rates of hydraulic pouches constructed in the form of a multilayered conical spiral using the latissimus dorsi muscle of 17 beagles. The roles that electrical muscle conditioning and early interruption of collateral blood supply have in the prevention of pouch fatigue were evaluated. The length of time that a pouch could generate flow in a hydraulic test system was measured; afterload was set at 80 mm Hg and preload 24 mm Hg. Pouches (N = 3) fashioned from muscles subject to neither electrical conditioning nor a vascular delay generated an initial flow of 990 +/- 346 ml/min, but could sustain flow for only 2.3, 3.8 and 3.6 minutes. Pouches (N = 5) constructed with electrically unconditioned muscles after a vascular delay (median 3 weeks) demonstrated a variable improvement in fatigue rates (initial flow 826 +/- 265 ml/min; time to no forward flow, 2.5, 7.5, 7.5, 10, and 200 minutes). Four of six pouches that received the benefit of long-term electrical muscle conditioning and a vascular delay (N = 6) were able to generate flow for a 4 hour period, at which time the experiment was terminated (initial flow 478 +/- 204 ml/min; final flow 195 +/- 157 ml/min). After the 4 hour fatigue test was completed, one electrically conditioned pouch was placed in series with the heart and served as a counterpulsator. The initial volume of blood pumped by the muscle pouch was 262 ml/min or 13.8% of cardiac output. After the pouch had contracted at a rate of approximately 45 beats/min for 1 hour, the volume of blood pumped was 178 ml/min, or 11% of cardiac output. In three other animals a pouch was fashioned and then left in situ for a 1 to 3 week period before hydraulic testing. These pouches generated significant initial flows (390 +/- 60 ml/min), which demonstrates the feasibility of further study of permanent pouches. These results suggest that permanent electrical muscle conditioning and perhaps a vascular collateral delay might permit an auxiliary skeletal muscle-powered ventricle to assume a portion of left ventricular function.     

A case of cardiomyoplasty with synchronous stimulated latissimus dorsi muscle

In December, 1988, a 57-year-old man sustained an acute myocardial infarction. He suffered from progressive cardiac failure, despite bed rest and intensive medical treatment. Finally, he developed hepatic and renal failure. Subsequent angiographic studies revealed the total occluded LAD (Seg. 6) and a large LV aneurysm. In January 1989, a left ventricular aneurysmectomy and cardiomyoplasty using the latissimus dorsi muscle were performed successfully. Two years after the operation, he is alive and well.     

Growth factors improve latissimus dorsi muscle vascularization and trophicity after cardiomyoplasty

BACKGROUND: Dynamic cardiomyoplasty consists of wrapping the electrostimulated latissimus dorsi muscle (LDM) around the failed heart. Partial ischemia followed by atrophy of the middle and distal part of the LDM were observed in 30% of clinical cases after LDM flap elevation from its origin. In the current study, we hypothesized that local administration of growth factors at the LDM/epicardial interface could improve muscle vascularization and trophicity. METHODS: In 24 sheep, dynamic cardiomyoplasty was performed using the left LDM. A multiperforated catheter was positioned at the LDM/epicardial interface for a weekly administration, during a 1-month period, of the following factors: basic fibroblast growth factor (bFGF, n = 6), vascular endothelial growth factor (VEGF, n = 6), and regenerating agent (RGTA, n = 6). Six sheep injected with phosphate-buffered saline (used for dilution of the growth factors) were used as a control group. At 3 months, angiographic, histologic, and histomorphometric studies were performed. RESULTS: Angiographic studies of the animals treated with growth factors demonstrated hypervascularization due to the development of new vessels. Histomorphometric and histologic studies showed a significant increase in the number of capillaries and arterioles (100 fields/muscle) in the groups treated with bFGF (443.0 +/- 101.2, p < 0.01), RGTA (293.2 +/- 29.3, p < 0.05), and VEGF (246.5 +/- 45.9, p < 0.05), as compared with the control group (81.5 +/- 11.4). A significantly lower atrophy score was observed in the groups treated with bFGF (1.4 +/- 0.18, p < 0.05), RGTA (1.59 +/- 0.17, p < 0.05), and VEGF (1.96 +/- 0.14, NS), as compared with the control group (2.48 +/- 0.16). CONCLUSIONS: Local administration at the heart/muscle interface of growth factors increases muscle vascularization and avoids muscle atrophy in an experimental cardiomyoplasty model, both of which are advantageous to the contracting LDM. The local growth factors delivery system used in this study appears efficient, easy to implant, and manipulate and safe.     

Activity–rest stimulation of latissimus dorsi for cardiomyoplasty: 1-year results in sheep

Background. In dynamic cardiomyoplasty electrostimulation achieves full transformation of the latissimus dorsi (LD); therefore, its slowness limits the systolic support. Daily activity–rest could maintain partial transformation of the LD.

Methods. Sheep LD were burst-stimulated either 10 or 24 hours/day. Before and 2, 4, 6, and 12 months after stimulation, LD power output, fatigue resistance, and tetanic fusion frequency were assessed. Latissimus dorsi were biopsied at 6 months, and sheep sacrificed at 12 months.

Results. After 1 year of 10 hours/day stimulation LD was substantially conserved and contained large amounts of fast type myosin. From 2 months to 1 year of stimulation the power per muscle of the daily rested LD was greater than that of the left ventricle, being three to four times higher than in the 24-hour/day stimulation.

Conclusions. If extended to humans, these results could be the rationale for the need of a cardiomyostimulator, whose discontinuous activity could offer to patients the long-standing advantage of a faster and powerful muscle contraction.     

Anatomic topographic study of the latissimus dorsi muscle of the spine in relation to cardiomyoplasty

The results of an anatomo-topographical study of the latissimus dorsi muscle in relation to surgery for cardiomyoplasty are discussed. The vascular anatomy of 25 flaps formed from the muscle were studied on the basis of the findings of angiography. The results allowed the conclusion that the latissimus dorsi muscle can be used as a transplant in operation for cardiomyoplasty.     

Effects of dynamic cardiomyoplasty on left ventricular performance and myocardial mechanics in dilated cardiomyopathy

We tested the hypothesis that dynamic cardiomyoplasty produces beneficial changes in the functional mechanics of the dilated, failing left ventricle. Chronic dilated cardiomyopathy was induced in seven mongrel dogs by rapid ventricular pacing (260 beats/min) for 3 to 4 weeks. After completion of the induction period, dynamic cardiomyoplasty was performed with the left latissimus dorsi muscle, paced synchronously with the R waves of the electrocardiogram (Medtronic SP1005). Instruments included an aortic flow probe, a left ventricular Millar pressure catheter, and piezoelectric sonomicrometric crystals on the left ventricle for measurements of wall thickness and minor and major axis dimensions. Data were obtained with the stimulator off and on. Statistical comparisons were made with Student's t test for paired data. Dynamic cardiomyoplasty increased the cardiac output of the failing heart (966 +/- 124 versus 1166 +/- 112 ml/min; p less than 0.01). Systolic shortening of both minor and major axis dimensions increased (3.1 +/- 0.3 versus 4.7 +/- 0.3 mm, p less than 0.01, and 4.6 +/- 0.3 versus 7.3 +/- 0.9 mm, p less than 0.05, respectively). Left ventricular end-diastolic pressure decreased by 16% (18 +/- 1 versus 15 +/- 1 mm Hg, p less than 0.01). Although skeletal muscle contraction increased the pressure development in the left ventricular chamber, mean systolic wall stress was diminished by concomitant changes in left ventricular dimensions (116,144 +/- 11,530 versus 101,268 +/- 7464 dynes/cm2, p less than 0.05). At end-systole, wall thickness increased (11.8 +/- 1.1 versus 12.7 +/- 1.1 mm, p less than 0.01), minor axis dimension decreased (51.3 +/- 1.4 versus 49.2 +/- 1.8 mm, p less than 0.01), and major axis dimension also decreased (85.6 +/- 3.3 versus 79.0 +/- 2.3 mm, p less than 0.05). Our detailed evaluation of left ventricular chamber mechanics suggests that dynamic cardiomyoplasty may have a role in ameliorating the functional and mechanical derangements associated with progression of dilated cardiomyopathy both by augmenting cardiac performance and by diminishing determinants of myocardial oxygen consumption. (All values are expressed as mean +/- standard error of the mean.)     

Left ventricular cardiomyoplasty by the use of a free latissimus dorsi myograft with a vascular anastomosis--augmentation of regional cardiac performance in dyskinetic segments

This study was performed to evaluate the ability of a free revascularized Latissimus Dorsi (LD) graft placed on dyskinetic segments of the left ventricle to augment regional left ventricular performance in 8 adult dogs. LD muscles preconditioned for 30 days were revascularized with the internal mammary artery and right atrial appendage. The free graft was sutured on the ischemic area of the left ventricular anterolateral wall, produced by ligation of the left anterior descending coronary artery. Grafts were paced at a burst frequency of 25 and 50 Hz, at a synchronization ratio of 1:1, 2:1, and 3:1. Effects of synchronously paced LD grafts on regional myocardial performance and hemodynamics were evaluated by placing ultrasonic crystals on the ischemic area and hemodynamic parameters. The flow rate of revascularized thoracodorsal artery (TDA flow) was measured during synchronously pacing of the grafts. Systolic bulging was shown in the ischemic area without graft pacing: %shortening (%S) = -9.5 +/- 3.6%. Graft pacing at a burst frequency of 25 and 50 Hz resulted passive segmental shortening of the ischemic left ventricular myocardium: %S = +3.9 +/- 1.9% (p less than 0.01, vs values without pacing) and +5.5 +/- 1.9% (p less than 0.01, vs values without pacing), respectively. The left ventricular pressure increased from 74 +/- 14 mmHg to 83 +/- 15 mmHg (p less than 0.01) with graft pacing at a burst frequency of 50 Hz. The peak aortic flow also was augmented by an average of 30 +/- 6% at paced cardiac cycles. The pattern of TDA flow during 1:1 synchronous pacing was changed to be dominant in diastolic, unlike the pattern without graft pacing. Values of TDA flow rate, however, increased after the initiation of pacing and reached 270 +/- 38% of control values. In conclusions, this study shows that a revascularized free LD graft has an ability to contract in systole against the left ventricular wall stress, and to augment regional left ventricular performance in dyskinetic segments. And sufficient blood perfusion to the grafts can be maintained during synchronously pacing of the grafts in cardiac systole.     

Dynamic cardiomyoplasty acutely impairs left ventricular diastolic function.

In patients with congestive heart failure, medical treatment has a high rate of mortality and morbidity, and transplantation is limited by the availability of donor hearts. Dynamic cardiomyoplasty is being investigated as surgical therapy to improve left ventricular function in these patients. To evaluate the early postoperative effects of this procedure on left ventricular diastolic function, we studied seven dogs through the use of sonomicrometry and micromanometry in a canine model of dynamic cardiomyoplasty. Left ventricular diastolic parameters were determined before wrapping the latissimus dorsi muscle (baseline), after latissimus dorsi muscle wrap but without stimulation, and with synchronous left ventricular contraction-latissimus dorsi muscle stimulation. End-diastolic pressure was increased in both conditions after latissimus dorsi muscle wrap (without stimulation, 5 +/- 1; with stimulation, 6 +/- 2 mm Hg; p < 0.05) compared with baseline (3 +/- 2 mm Hg). The peak rate of diastolic pressure decay was greater at baseline (1560 +/- 370 mm Hg/sec) than after latissimus dorsi muscle wrap, both without (1260 +/- 330 mm Hg/sec, p < 0.01) and with (1120 +/- 420 mm Hg/sec, p < 0.01) stimulation. The constant of pressure decay was prolonged both without (53 +/- 10 seconds, p < 0.05) and with (62 +/- 11 seconds, p < 0.01) latissimus dorsi muscle stimulation compared with the baseline (38 +/- 5 seconds). Compared with baseline (0.2 +/- 0.2 cm-2), the constant of passive chamber stiffness increased after the latissimus dorsi muscle was wrapped around the heart (1.6 +/- 0.7 cm-2, p < 0.05) and with stimulation (2.1 +/- 1.0 cm-2, p < 0.01). The maximal diastolic filling rate (baseline, 18.1 +/- 6.7; without stimulation, 16.6 +/- 8.9; with stimulation, 16.6 +/- 4.1 cm2/sec, not significant) and end-diastolic short-axis area (baseline, 7.3 +/- 2.3; without stimulation, 7.4 +/- 2.1; with stimulation, 7.5 +/- 2.3 cm2, not significant) were similar among the three conditions. The latissimus dorsi muscle wrap prolonged relaxation and increased left ventricular passive stiffness. Synchronous latissimus dorsi muscle stimulation with left ventricular contraction did not improve diastolic function in this model. The results suggest that in the early postoperative period, dynamic cardiomyoplasty impairs diastolic function.