Automated distal coronary bypass with a novel magnetic coupler (MVP system).

OBJECTIVE: We sought to assess the feasibility of performing sutureless distal coronary artery bypass anastomoses with a novel magnetic coupling device. METHODS: From May 2000 to April 2001, single-vessel side-to-side coronary artery bypass grafting on a beating heart was performed in 39 domestic white pigs (35-60 kg) without the use of mechanical stabilization, shunts, or perfusion bridges. Animals were divided into 2 groups. Seventeen pigs underwent right internal thoracic artery to right coronary artery bypass grafting through a median sternotomy (group 1) with a novel magnetic vascular positioning system (MVP system; Ventrica, Inc, Fremont, Calif). Twenty-two pigs underwent left internal thoracic artery to left anterior descending artery grafting with the MVP anastomotic device through a left anterior minithoracotomy (group 2). This system consists of 2 pairs of elliptical magnetic implants and a deployment device. One pair of magnets forms the anastomotic docking port within the graft; the other pair forms an identical anastomotic docking port within the target vessel. The anastomosis is created when the 2 docking ports magnetically couple. Anastomotic patency was evaluated by means of angiography during the first postoperative week and at 1 month. Histologic studies were performed at different time points as late as 6 months. RESULTS: Right internal thoracic artery to right coronary artery anastomoses and left internal thoracic artery to left anterior descending artery anastomoses were successfully performed with the system in all animals. The self-adherent and self-aligning properties of the implants allowed for immediate and secure approximation of the arteries (total anastomotic time between 2-3 minutes). Anastomoses were constructed without a stabilization platform. Five nondevice-related deaths occurred postoperatively. One-week angiography, performed in 35 surviving animals, showed a patent graft and anastomosis in all cases. The patency rate at 1 month was 97% (33/34). Histologic studies as late as 6 months demonstrated neointimal coverage of the magnets without any significant luminal obstruction. Histology also confirmed the presence of viable tissue between magnets. CONCLUSION: The MVP anastomotic system uses magnetic force to create rapid and secure distal coronary artery anastomoses, which might facilitate minimally invasive and totally endoscopic coronary artery bypass surgery.

Mitral valve repair in redo cardiac surgery.

An increasing number of patients are being referred for mitral valve repair in the redo cardiac surgery setting. The most common clinical scenarios involve prior coronary bypass surgery or aortic valve replacement, each presenting special challenges in terms of gaining valve exposure to enable repair while limiting dissection as much as possible. A right anterior thoracotomy approach is preferred in most patients, coupled with hypothermic fibrillatory arrest. A repeat sternotomy may be favored in select circumstances such as when there is a need for bypass grafting or moderate aortic insufficiency is present. Special attention to cannulation techniques, perfusion conditions, valve exposure, and de-airing maneuvers are all important to ensure good clinical results. Using a tailored approach we have performed mitral valve repair in 22 patients with a patent left internal mammary artery graft following coronary artery bypass grafting between July 1992 and February 2000 with acceptable morbidity and low mortality.

Minimally invasive CABG.

For more than three decades, conventional coronary artery bypass grafting (full sternotomy, cardiopulmonary bypass, and cardioplegic arrest) has been the treatment of choice for patients with multi-vessel coronary artery disease. However, neurologic injury secondary to ascending aortic manipulation and systemic inflammatory reaction related to cardiopulmonary bypass are major causes of morbidity. During the past decade research efforts have been focused on the development of innovative revascularization techniques to minimize these deleterious effects. Minimally invasive direct coronary artery bypass surgery was developed to reduce chest trauma and to accelerate patient recovery. The relatively recent introduction of mechanical stabilizers and positioning devices has allowed for the safe performance of off-pump coronary artery bypass for patients with multi-vessel disease. Robotic technology has offered the possibility of myocardial revascularization through limited access using endoscopic principles. Recently, emphasis has been placed on the development of new sutureless anastomotic devices that may revolutionize the field of myocardial revascularization and allow a broader acceptance of minimally invasive CABG. Despite the increasing availability of new technologies, the validity of these procedures must be evaluated carefully. Prospective randomized studies and longitudinal follow-up will be required.

The preferred approach for mitral valve surgery after CABG: right thoracotomy, hypothermia and avoidance of LIMA-LAD graft.

BACKGROUND AND AIM OF THE STUDY: An alternative to avoid redo sternotomy in patients with patent left internal mammary artery-left anterior descending coronary artery (LIMA-LAD) grafts undergoing mitral valve surgery is right thoracotomy with moderate-deep hypothermia (approximately 20 degrees C) and fibrillatory arrest without aortic cross-clamping. Few reports exist which directly compare re-sternotomy and right thoracotomy. METHODS: Between July 1992 and February 2000, 47 patients (39 males, eight females; median age 66 years; range: 41-83 years; 41 in NYHA class III or IV) with patent LIMA-LAD grafts underwent mitral valve surgery. Thirty-seven patients were approached through a right thoracotomy with moderate-deep hypothermia (median 20 degrees C) and fibrillatory arrest (right thoracotomy group), and 10 were approached through a re-sternotomy, with aortic cross-clamping and cardioplegic arrest. The median ejection fraction was 42% (range: 20-71%). Univariate analysis was used to determine predictors of outcome, as well as to evaluate differences in characteristics between groups. RESULTS: Operative mortality (OM) and perioperative myocardial infarction for the entire cohort was 11% and 10%, respectively, and there were no inter-group differences. No preoperative characteristics were associated with OM. Two LIMA-LAD graft injuries occurred in the re-sternotomy group compared with none in the right thoracotomy group (20% versus 0%, p = 0.04). Transfusion requirements were also greater in the redo sternotomy group (median 7 versus 2 packed red blood cell units, p = 0.04). CONCLUSION: Right thoracotomy with moderate-deep hypothermia and fibrillatory arrest is the preferred approach for reoperative mitral valve surgery after coronary artery bypass grafting in the presence of patent LIMA-LAD grafts. These data suggest that this approach is associated with decreased incidence of LIMA-LAD graft injury, as well as reduced transfusion requirements.

Does coronary artery bypass grafting alone correct moderate ischemic mitral regurgitation?

BACKGROUND: The optimal management of moderate (3+ on a scale of 0 to 4+) ischemic mitral regurgitation (MR) remains controversial. Some advocate CABG alone, whereas others favor concomitant mitral annuloplasty. To clarify the optimal management of these patients, we evaluated the early impact of isolated CABG on moderate ischemic MR. METHODS AND RESULTS: Between January 1992 and August 1999, 136 patients (54% male, mean age 70.5 years, mean New York Heart Association class 2.7, mean ejection fraction 38.1%) with a preoperative diagnosis of moderate ischemic MR, without leaflet prolapse or pathology, underwent isolated CABG. Thirty-eight (28%) of 136 patients had intraoperative transesophageal echocardiography (TEE) before CABG, and 68 (50%) had postoperative transthoracic echocardiography (TTE) within 6 weeks of surgery. The subgroups of patients undergoing intraoperative TEE and postoperative TTE had preoperative characteristics similar to the overall group. The 30-day operative mortality was 2.9% (). Intraoperative TEE downgraded the severity of MR to mild or less (0 to 2+) in 89% (). On postoperative TTE, 40% () continued to have at least moderate MR (3 to 4+), 51% () improved somewhat to mild (2+) MR, and only 9% () had resolution of their MR (0 to 1+). The mean preoperative, intraoperative, and postoperative MR grades were 3.0+/-0.0, 1.4+/-1.0, and 2.3+/-0.8, respectively (P<0.001). CONCLUSIONS: CABG alone for moderate ischemic MR leaves many patients with significant residual MR and may not be the optimal therapy for most patients. Intraoperative TEE may significantly underestimate the severity of ischemic MR. A preoperative diagnosis of moderate MR may warrant concomitant mitral annuloplasty.

Aortic valve reoperation after homograft or autograft replacement.

BACKGROUND AND AIM OF THE STUDY: With increasing use of homograft and autograft aortic valves for aortic valve replacement (AVR), more patients will be presenting for aortic valve reoperation due to structural degeneration of the homograft or autograft valve. Management options include homograft re-replacement, which may require extensive surgery, versus AVR with a mechanical valve or a stented xenograft. Here, results are reported in 18 consecutive patients who underwent aortic valve re-replacement (AVreR) after previous homograft or autograft insertion. METHODS: Between May 1976 and March 2001, 18 patients underwent AVR after previous homograft (n = 16) or autograft (n = 2) insertion. The homograft or autograft had been implanted as a full root in eight patients (44%), as a mini-root in one (6%), and in the subcoronary position in nine (50%). Indication for the reoperation was structural valve degeneration (n = 14; 72%) in one occasion combined with aneurysm of the homograft, or endocarditis (n = 4; 22%), and seven (39%) presented as a non-elective procedure. The median interval between the two operations was 5.4 years (range: 0.3-10.8 years). RESULTS: Fourteen patients (78%) received either a mechanical valve (n = 12; 67%) or a stented xenograft valve (n = 2; 11%). Four others (22%) required root re-replacement with either another homograft (n = 3) or a mechanical valved conduit (n = 1) for endocarditis (n = 2) or an associated aneurysm (n = 2). Overall hospital mortality was 11% (n = 2) due to stroke (n = 1) or respiratory failure (n = 1). Two patients died 3.1 and 7.0 years after the procedure. CONCLUSION: Aortic valve reoperation after previous homograft or autograft implantation is a rare operation and presents a high-risk group. A simplified approach was preferred by utilizing mechanical or stented xenograft valves at reoperation, while homograft re-replacement was reserved for endocarditis or an associated aneurysm.

Modified Glenn connection for acutely ischemic right ventricular failure reverses secondary left ventricular dysfunction.

BACKGROUND: Right heart failure after cardiopulmonary bypass can result in severe hemodynamic compromise with high mortality, but the underlying mechanisms remain poorly understood. After ischemia-induced right ventricular failure, alterations in the interventricular septal position decrease left ventricular compliance and limit filling but may also distort left ventricular geometry and compromise contractility and relaxation. This study investigated the effect of acute isolated right ventricular ischemia on biventricular performance and interaction and the response of subsequent right ventricular unloading by use of a modified Glenn shunt. METHODS: In 8 pigs isolated right ventricular ischemic failure was induced by means of selective coronary ligation. A modified Glenn circuit was then established by a superior vena cava-pulmonary artery connection. Ventricular performance was determined by conductance catheter-derived right ventricular pressure-volume loops and left ventricular pressure-segment length loops. Hemodynamic data at baseline, after right ventricular ischemia, and after institution of the Glenn circuit were obtained during inflow occlusion, and the load-independent contractile indices were derived. RESULTS: Right ventricular free-wall ischemia resulted in acute right ventricular dilation (118 +/- 81 mL vs 169 +/- 70 mL, P =.0008) and impairment of left ventricular contractility indicated by the reduced end-systolic pressure-volume relation slope (50.0 +/- 19 mm Hg/mm vs 18.9 +/- 8 mm Hg/mm, P =.002) and preload recruitable stroke work index slope (69.6 +/- 26 erg x cm(-3) x 10(3) vs 39.7 +/- 13 erg x cm(-3) x 10(3), P =.003). In addition, left ventricular relaxation (tau) was significantly prolonged (33.3 +/- 10 ms vs 53.0 +/- 16 ms, P =.012). Right ventricular unloading with the Glenn shunt reduced right ventricular dilation and significantly improved left ventricular contraction, end-systolic pressure-volume relation slope (18.9 +/- 8 mm Hg/mm vs 35.8 +/- 18 mm Hg/mm, P =.002), preload recruitable stroke work index slope (39.7 +/- 26 erg x cm(-3) x 10(3) vs 63.0 +/- 22 erg x cm(-3) x 10(3), P =.003), and diastolic performance (tau 53.0 +/- 16 ms vs 43.5 +/- 13 ms, P =.001). CONCLUSIONS: Right ventricular ischemia-induced dilation resulted in acute impairment of left ventricular contractility and relaxation. A modified Glenn shunt attenuated the left ventricular dysfunction by limiting right ventricular dilation and restoring left ventricular cavity geometry.

Reoperative CABG using left thoracotomy: a tailored strategy.

BACKGROUND: Reoperative coronary artery bypass grafting (CABG) through a left thoracotomy is a challenging operation with no one dominant approach. We developed a tailored strategy for this difficult group of patients, integrating the currently available newer technologies for each patient indication. METHODS: Between October 1991 and October 1999, 50 consecutive patients underwent reoperative CABG through a left thoracotomy. Age was 65 +/- 9 years, 40 (80%) were men, and preoperative ejection fraction was 40 +/- 13. In 36 patients (72%) the left internal mammary artery had been placed to the left anterior descending coronary artery during the primary CABG and in 25 of 36 patients (70%) this left internal mammary artery-left anterior descending coronary artery graft was patent. The mean duration from previous CABG was 8.0 +/- 4.8 years. Three approaches were used: (1) conventional cardiopulmonary bypass using fibrillatory or circulatory arrest (n = 33, 66%); (2) Heartport endoaortic balloon occlusion (n = 4, 8%); and (3) off-pump beating heart techniques (n = 13, 26%). RESULTS: The off-pump CABG technique was used in the majority of recent patients and 1 (7.7%) had to be converted to cardiopulmonary bypass due to hemodynamic instability. When cardiopulmonary bypass was used its duration was 122 +/- 59 minutes and mean temperature on bypass was 24 degrees +/- 6 degrees C. In the 4 patients in whom the Heartport system was used, the median endoaortic occlusion duration was 49 minutes. Patients received an average of 1.4 grafts/patient. In 60 of 70 patients (89%) distal anastomoses were performed to an anterolateral coronary target. There were 3 of 50 (6%) operative deaths, 2 in the conventional group and 1 in the endoaortic balloon occlusion group. The mean length of stay in the 47 survivors was 7.8 +/- 3.9 days (median, 7 days). CONCLUSIONS: Reoperative CABG by left thoracotomy remains a challenging operation. Several techniques, including off-pump CABG, conventional cardiopulmonary bypass, circulatory arrest, and endoaortic balloon occlusion, should be in the surgeon's armamentarium to allow a tailored approach for each operation based on patient indications.

Emergency surgical pulmonary embolectomy.

Emergency surgical pulmonary embolectomy is a highly effective treatment for selected patients with pulmonary embolism. Rapid noninvasive diagnostic modalities allow proper patient selection based on anatomic location of the emboli, right heart function, and contraindications to thrombolysis. Operative results are a direct reflection of the preoperative hemodynamic status, the degree of underlying cardiopulmonary disease, and attention to minimizing surgical trauma and protecting the right heart. An operative mortality of 10% or less and excellent long-term outcomes can be expected if the procedure is performed prior to cardiovascular collapse as part of a multidisciplinary strategy which emphasizes careful patient selection, rapid diagnosis, triage, and transport.

Partial upper re-sternotomy for aortic valve replacement or re-replacement after previous cardiac surgery.

OBJECTIVE: We developed techniques for 'inverted T' partial upper re-sternotomy for aortic valve replacement (AVR) or re-replacement (AVreR) after previous cardiac surgery. We previously reported on decreased blood loss, transfusion requirements and total operative duration when compared to conventional full re-sternotomy. This report updates our series, one of the few to document a substantial benefit from a 'minimally-invasive' approach, refines a number of technical aspects of this new approach and reports follow-up. METHODS: Between November 1996 and December 1999, we performed 34 AVRs or AVreRs after previous cardiac surgery by use of an 'inverted T' partial upper re-sternotomy. There were 25 (74%) men. Median ejection fraction was 54%, range 15-80%. Median age was 72, range 38-93. All were New York Heart Association functional class (NYHA) functional class II or III. Twenty-one (62%) had previous coronary artery bypass grafts (CABG) while 14 (41%) had previous valve surgery. Follow-up was 100% complete for a total of 593 patient months (median 19 months). RESULTS: Twenty-three (66%) underwent AVR of the native aortic valve while 11 (33%) underwent AVreR of a prosthetic aortic valve. There were no intraoperative or valve-related complications, and no conversion to full re-sternotomy was necessary. There were two (5.9%) operative deaths from an arrhythmia on postoperative day 4 and a large stroke during surgery, respectively. Twenty-four (75%) patients were free of major complications. There was no need for reoperation for bleeding and patients required a median of two units of packed red blood cells. Complications included new atrial fibrillation (n=3, 9%), pacemaker implantation (n=3, 9%) and deep sternal wound infection (n=2, 6%). Median lengths of stay in the intensive care unit (ICU) and in the hospital were 1 and 7 days, respectively. There was one (3%) late deep sternal wound infection and 2/32 (6%) late deaths due to congestive heart failure at 22 months and myocardial infarction at 23 months, respectively. CONCLUSIONS: Partial upper re-sternotomy presents a safe and effective alternative approach to AVR and AVreR after previous cardiac surgery, and is associated with low morbidity and mortality.

Pulmonary autograft versus aortic homograft for aortic valve replacement: interim results from a prospective randomized trial.

BACKGROUND AND AIM OF THE STUDY: Although pulmonary autografts offer advantages over aortic homografts, they may also carry additional risks. We reviewed the interim results of a prospective randomized trial of autograft versus homograft aortic valve replacement (AVR) to determine if the greater complexity of the autograft insertion is justified, particularly with regard to time-related hemodynamic function. METHODS: A total of 182 patients (82% male, 18% female; mean age 37.2 +/- 14.3 years; range: 2-64 years) with isolated aortic valve disease were randomized to pulmonary autograft (group A, n = 97) or aortic homograft (group H, n = 85); 42% had previous aortic valve surgery and 19% had native or prosthetic valve endocarditis. Follow up included annual outpatient visits and echocardiography. RESULTS: Autograft AVR required longer cross-clamp (41%) and bypass (43%) times, but did not result in significantly more bleeding, longer recovery or more complications. One 30-day death occurred in group A (1%), and three deaths in group H (4%). Median follow up was 33.9 months (range: 1-61 months). There was one late death in each group, three reoperations in group A (all for pulmonary homografts), and three in group H (including two aortic homograft reoperations, both in children). There were no autograft reoperations. There were no other valve-related events. At 48 months, actuarial survival and reoperation-free survival rates were 97.8% and 94.2% in group A, and 95.3% and 87.7% in group H (p = NS). Echocardiography showed near-perfect function in all autografts, but early signs of subclinical dysfunction in many homografts. CONCLUSION: Both autograft and homograft AVR are safe and produce good intermediate-term results. Early homograft degeneration appears to favor autografts in children. The echocardiographic findings may translate into superior long-term autograft durability and hemodynamics.

Minimally invasive direct access heart valve surgery.

We review our experience with minimally invasive direct access (MIDA) heart valve surgery in 518 patients. Two hundred fifty-two patients underwent MIDA aortic valve replacement (AVR) or repair and 266 underwent MIDA mitral valve repair or replacement. Among the 250 AVRs, 157 (63%) were men, aged 63.2 +/- 14.6 years, NYHA functional Class 2.4 +/- 0.8. The surgical approach was right parasternal in 36 (14%) or upper hemisternotomy in 216 (86%). There were four (2%) operative deaths. Perioperative complications included 14 (5.6%) reexplorations for bleeding, 7 (3%) chest wound infections, 5 (2%) strokes, and 1 (0.4%) external iliac vein injury. Follow-up was complete in 193 (77%) patients, with a mean follow-up of 12 +/- 8 months. Late complications included 2 (0.8%) nonfatal myocardial infarctions, 4 (2%) reoperations for, respectively, 2 pericardial complications, 1 paravalvar leak, and 1 infected valve. There were five (2%) late deaths from congestive heart failure, pneumonia, hemorrhage, aneurysm, and cancer. Mean follow-up NYHA Class was 1.4 +/- 0.6. For the 266 mitral patients, 145 (54.5%) were men, age 58.7 +/- 13.6 years, functional Class 2.3 +/- 0.5. The surgical approach was right parasternal in 195 (73%), lower hemisternotomy in 53 (20%), right submammary thoracotomy in 9 (3.4%), or full sternotomy through a small skin incision in 9 (3.4%). There were 2 (0.8%) operative deaths. Perioperative complications included 4 (1.5%) reoperations for bleeding, 4 (1.5%) strokes, and 5 (2%) wound infections, and 3 (1%) ascending aortic complications. Follow-up was complete in 202 (76%) patients with a mean follow-up of 9.5 +/- 6.4 months. Late complications included one (0.4%) nonfatal myocardial infarction and three (1%) reoperations all converting repairs to replacements. There were three (1%) late deaths from suicide, pneumonia, and sudden death, respectively. Mean follow-up NYHA functional Class was 1.3 +/- 0.5. We conclude that MIDA heart valve surgery is safe and effective for the majority of patients requiring isolated elective aortic or mitral valve surgery.

Techniques and results of direct-access minimally invasive mitral valve surgery: a paradigm for the future.

OBJECTIVES: Our objective was to determine whether direct-access minimally invasive mitral valve surgery can improve recovery and cost while maintaining the efficacy of conventional surgery. METHODS: Minimally invasive mitral valve operations were performed on 106 patients, 58% male, average age 58.1 years, with good ventricular function. Ninety underwent repair of a regurgitant, myxomatous valve, and 16 underwent mitral valvuloplasty for prematurely calcified mitral stenosis. The valve was approached with standard instruments through a 5- to 8-cm right parasternal incision. Eighty-five had open femoral artery-femoral vein cannulation, but this technique has recently been replaced by direct cannulation of the aorta and percutaneous cannulation of the femoral vein for most patients. RESULTS: There were no operative deaths. The mean mitral regurgitation score (0-4) decreased from 3.7 to 0.7 after the operation. Although ischemic and bypass times were increased, postoperative recovery was accelerated. Ventilatory support time, intensive care unit stay, hospital stay, need for rehabilitation, and return to "normal activities" all improved. Hospital charges, pain medications, and blood transfusions were also reduced. New atrial fibrillation contributed significantly to increased length of stay and charges. There were no deep wound infections. Other complications included re-exploration for bleeding (n = 1), transient ischemic attacks (n = 2), stroke (n = 1), femoral artery injury (n = 5), pseudoaneurysm (n = 2), and antegrade dissection of the ascending aorta (n = 1). Two patients died and 1 required reoperation during a mean follow-up of 8.8 months. CONCLUSIONS: Direct-access minimally invasive mitral valve surgery can accelerate recovery, decrease charges, and decrease pain, while maintaining overall surgical efficacy. It has become our standard approach for isolated primary mitral valve operations.

An engineering model of dynamic cardiomyoplasty. I.

Dynamic cardiomyoplasty (DCM) is an emerging surgical procedure for heart failure in which the patient's latissimus dorsi (LD) muscle is wrapped around the heart and stimulated to contract in synchrony with the heartbeat as a cardiac assist measure. A 6 week training protocol of progressive electrical stimulation renders the normally fatigueable skeletal muscle fatigue-resistant and suitable for chronic stimulation. To date, over 500 procedures have been performed in worldwide clinical trials. Investigators typically report symptomatic improvement and modest hemodynamic improvement in patients. Controversy exists regarding the exact mechanism of DCM. To test the hypothesis that DCM augments cardiac stroke volume through improvement in systolic function, we formulated an engineering model of dynamic cardiomyoplasty to predict stroke volume. The heart and the LD were modeled as nested (series) elastance chambers, and the vasculature was represented by a two-element Windkessel model. Using five healthy goats, we verified model predictions of stroke volume for both stimulator ON beats (y = 1.00x-0.08, r = 0.87, p < 0.0001) and OFF beats (y = 1.01x+1.06, r = 0.91, p < 0.0001), where x and y are the measured and predicted stroke volumes, respectively. The model confirms that using untrained latissimus dorsi applied to the normal myocardium produces only moderate increases in stroke volume and suggests that future research should focus on increasing LD strength after training.

An engineering model of dynamic cardiomyoplasty. II. Clinical applications.

Previously, a modification to the Sunagawa engineering model for the isolated left ventricle and arterial system was proposed and validated for dynamic cardiomyoplasty in an acute goat preparation. To test the hypothesis that this model may be applied to the clinical scenario in cardiomyoplasty patients, we predicted human stroke volume using the model with human clinical data from the literature. Predicted stroke volume correlated well with published stroke volume in patients who have had the dynamic cardiomyoplasty procedure. These results suggest that the modest hemodynamic improvement commonly reported after the procedure is performed may be due to diminished latissimus dorsi strength after transformation. The validity of both the original Sunagawa model and the previously proposed modification for dynamic cardiomyoplasty is further supported with these results. A nomogram methodology for predicting stroke volume after dynamic cardiomyoplasty for any particular patient is presented.

Right latissimus dorsi cardiomyoplasty improves left ventricular energetics.

BACKGROUND: The mechanism by which cardiomyoplasty appears to enhance left ventricular (LV) function is not well understood. We applied the time-varying elastance model to study the effect of cardiomyoplasty on LV function, ventriculovascular coupling, and LV energetics in an acute canine model. METHODS: Right latissimus dorsi cardiomyoplasty was performed in 5 dogs. The end-systolic pressure-volume relation was generated by using brief caval occlusions. End-systolic elastance, effective arterial elastance, stroke work, internal work, total mechanical work, and stroke work efficiency (stroke work/total mechanical work) were calculated from these pressure-volume data. Myocardial oxygen consumption and overall mechanical efficiency (stroke work/myocardial oxygen consumption) were predicted using the myocardial oxygen consumption-total mechanical work relation. RESULTS: Skeletal muscle contraction significantly increased end-systolic elastance, an index of contractility. Although stroke work did not change significantly, the increase in end-systolic elastance led to a 29% decrease in total mechanical work, a 50% decrease in internal work, and an increase in stroke work efficiency from 53% to 66%. This was consistent with the observed 29% decrease in effective arterial elastance/end-systolic elastance, an indicator of ventriculovascular coupling that is related inversely to stroke work efficiency. Predicted myocardial oxygen consumption decreased by at least 22%, and predicted overall mechanical efficiency increased at a minimum from 16.1% to 18.4%. CONCLUSIONS: These results support the theory that cardiomyoplasty unloads the LV by decreasing LV volumes and increasing contractility. These effects appear to improve LV energetics by decreasing total mechanical work without significantly affecting stroke work, resulting in improved stroke work efficiency. The decrease in total mechanical work strongly suggests a decrease in myocardial oxygen consumption and an increase in overall mechanical efficiency.