Asian Cardiovasc Thorac Ann 2002;10:264-266
© 2002 Asia Publishing EXchange Pte Ltd
Cardiomyoplasty: First Clinical Case With New Cardiomyostimulator
Valeri S Chekanov, MD,
Duane E Sands, MD1,
Conville S Brown, MD1,
Fernando Brum, MD2,
Pedro Arzuaga, MD2,
Sebastian Gava, MD2,
Ferdinand P Eugenio, MD2,
Vladimir Melamed, MD3,
Howard W Spencer, MD1
Heart Care Associates, Inc. Milwaukee Heart Institute at Aurora-Sinai Medical Center Milwaukee, Wisconsin, USA
1 The Bahamas Heart Center Nassau, Bahamas
2 Centro de Construccion de Cardioestimulatores del Uruguay Montevideo, Uruguay
3 Illini Group Chicago, Illinois, USA
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For reprint information contact: Valeri S Chekanov, MD Tel: 1 414 219 7899 Fax: 1 414 219 6266 email: ahcvch{at}execpc.com Heart Care Associates, Inc., Milwaukee Heart Institute at Aurora-Sinai Medical Center, 945 North 12th Street, Room W301, P.O. Box 342, Milwaukee WI 53201-0342, USA.
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ABSTRACT
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Dynamic cardiomyoplasty was performed in a patient using a new cardio-myostimulator (LD-PACE II) designed to enable a novel stimulation regimen that utilizes a new range of stimulation options, including cessation during sleep. After treatment, left ventricular ejection fraction improved in 24 months from 15% to 25% and New York Heart Association classification improved from class IV to II.
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INTRODUCTION
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Dynamic cardiomyoplasty (DCMP) is a procedure in which a subtotally mobilized latissimus dorsi muscle (LDM) is wrapped around the failing heart to augment its ventricular function through stimulation timed to cause the LDM to contract in synchrony with cardiac systole. In the past 14 years, DCMP has been performed over one thousand times. Potentially low risk, it has a mortality rate similar to those of other available means but yields improved clinical results.1 One study reported considerably higher actuarial survival rates (60%) after 54 months in the DCMP group than in the medically treated group (27%) for patients in New York Heart Association (NYHA) functional class III or intermittent class IV.2 Another reported similar actuarial survival rates at 2 years’ follow-up: 30% in medically treated patients versus 80% in DCMP patients.1
Most DCMP patients show improvement in daily activities and mental acuity,3 and NYHA class advanced from III or higher (3 to 3.6) to II or lower (1.6 to 2).1–3 One study reported that after 6 months of improvement, left ventricular ejection fraction (LVEF) slowly decreased, and it reverted to preoperative levels after 5 years.2 Conversely, another study found that after 3 years LVEF still exceeded preoperative levels, especially during exercise.4
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CASE REPORT
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A 57-year-old woman, with an 18-year history of known hypertension, presented with shortness of breath due to dilated cardiomyopathy. She was referred to the Bahamas Heart Center for treatment of unstable angina pectoris and associated congestive heart failure. Cardiac catheter-ization and coronary angiography revealed normal coronary arteries but left ventricular (LV) dilation with severe global hypokinesia, LVEF of 12%, and LV end-diastolic pressure of 40 mm Hg. Repeated 2-dimensional echocardiograms confirmed LV dilation (LV internal diameter of 6.3 cm during diastole) and global hypokinesia with LVEF of 15%. Her chest radiograph showed a cardiothoracic ratio of 0.6 to 0.65.
During DCMP performed in April 2000, with the patient in a right lateral decubitus position, a skin incision was made from the axillary region to the midpoint of the 12th rib along the anterior margin of the LDM. The LDM was dissected from all insertion points while carefully preserving the thoracodorsal neurovascular pedicle. All other vascular branches from the intercostal arteries were cut and ligated. The humeral tendon of the LDM was cut. After the LDM was subtotally mobilized, 2 muscle electrodes were placed in its proximal portion. The anterior third of the 2nd rib was removed, through which window the LDM was transferred into the left pleural cavity. The dissected tendon of the LDM was secured to the pericostal tissue of the excised rib to prevent traction and torsion of the neurovascular pedicle. The wound was then drained and closed in layers.
Next, the patient was placed in the supine position, and a median sternotomy was performed. A reversed U-shaped pericardial flap was created in front of the right ventricle (RV) for later augmentation of the ventricular wrapping. The LDM was retrieved from the left pleural cavity. One suture was placed proximally in the pericardium near the origin of the left pulmonary artery and another distally at the level of the diaphragm close to the inferior vena cava. These sutures were inserted through the edge of the LDM to fix the heart wrap. The heart was slightly elevated, and the muscle flap was positioned behind the left ventricle with care not to create torsion in the vascular supply.
The heart wrap was completed by suturing the edge of the muscle flap and positioning a pericardial flap in front of the RV. An epicardial sensing lead was placed in the RV. Cardiac sensing leads and muscular leads were tunneled to a site over the left upper rectus abdominis muscle and connected to a newly designed cardiomyostimulator LD-PACE II (Centro de Construccion de Cardioestimulatores del Uruguay, Montevideo, Uruguay). This device was placed in a subfascial pocket. Finally, the mediastinum was drained by 2 large-bore chest tubes, and the wound was closed in the usual fashion.
Following 2 weeks in which the patient was free of postoperative complications, electrical stimulation was initiated, employing the following protocol: 1 impulse per burst, 2.5 V, 35-msec ventricular-LDM delay, and a 1:2 cardiosynchronization ratio. One month later, the device was programmed to 3 impulses per burst, and LVEF improved to 25%. Two weeks later, programming to 4 impulses per burst improved LVEF to 30% and maintained this level during several months of follow-up.
Six months after DCMP, the cardiosynchronization ratio was changed from 1:2 to 1:4 to allow the LDM more time for rest. LVEF remained at 25% to 30%. LV internal diameter during diastole decreased from 6.3 cm before the operation to 5.5 cm. Ten months postoperatively, hemodynamic function had not significantly decreased nor was clinical status aggravated, but LVEF fell to 22%. The patient did not experience shortness of breath, fatigue, or chest discomfort, and she was recategorized as NYHA class II.
At that point, by means of a magnet wand, the stimulator was programmed to be switched off at night and switched back on during the day at a ratio of 1:4. Two months later, LVEF increased to 25%, and chest radiography revealed a cardiothoracic ratio of 0.55 to 0.6 (slightly less than before DCMP, attributed to the heart wrap’s increasing the size of the heart muscle complex). Twenty-four months after DCMP, the patient had an LVEF of 25%, continued to be free of shortness of breath, fatigue, or chest discomfort, and remained in NYHA class II.
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DISCUSSION
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The cardiomyostimulator was first developed and tested by Medtronic, Inc. (Minneapolis, MN, USA). A prospective randomly assigned phase III trial comparing DCMP patients with those receiving medical therapy found that the mortality rate decreased steadily after DCMP from over 20% in phase I trials to 12% in phase II and only 4% in phase III.5 Improvement by 1 or 2 NYHA classes 6 months after randomization was reported for 79% of DCMP patients, compared with 25% of medically treated patients.6
DCMP is an option especially for patients whose class III heart failure cannot be managed effectively with medication alone and yet who are not sick enough for a transplant. Cardiomyoplasty patients have been reported to have a higher quality of life than those treated by medication alone.7 Impressive clinical improvement can follow DCMP,8 making it a therapeutic option when cardiac transplantation is contraindicated.
The LD-PACE II, the new cardiomyostimulator employed in our case, incorporates features from findings gained through a decade of experimental and clinical investigation. It is slated to be used in cardiomyoplasty, aortomyoplasty, and skeletal muscle ventricle procedures. Experimental tests of its range of programming options and its first clinical use indicate that it can satisfy requirements for generating biological energy from skeletal muscle to achieve cardiac bioassist. Moreover, it may inspire further development in various approaches to cardiac bioassist, perhaps achieving the goal of sufficiently strengthening the heart of patients with severe heart failure so that they can continue life without a transplant.
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Acknowledgments
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The authors would like to acknowledge Rob Henderson for his editorial assistance.
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REFERENCES
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ABSTRACT
INTRODUCTION
