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Ann Thorac Surg 2002;74:1684-1685
© 2002 The Society of Thoracic Surgeons
a Department of Thoracic Cardiovascular Surgery, Heart Center North Rhine-Westphalia, Bad Oeynhausen, Germany
Accepted for publication June 28, 2002.
* Address reprint requests to Dr Omoto, Department of Thoracic Cardiovascular Surgery, Heart Center North Rhine-Westphalia, Bad Oeynhausen, Germany
e-mail: omota{at}kddnet.de
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A 70-year-old man had undergone coronary artery bypass grafting in 1984 after anterior wall infarction. Postoperatively, he had posterior wall infarction. He was admitted to our hospital in April 2000 because of deteriorating dyspnea. Clinical function was New York Heart Association class III. Electrocardiography showed complete left bundle branch block and QRS duration longer than 160 milliseconds. Echocardiography showed hypokinesis in the anterolateral wall and akinesis in the apex, septal wall, and posterior wall. Catheter angiography was performed. Diffuse atherosclerotic changes in the coronary arteries were found. Although bypass to the obtuse marginal branch was opened, bypass to the left anterior descending artery was occluded. Redo bypass operation to the left anterior descending artery was not indicated because of severe atherosclerotic changes. Cardiac index was 2.3 L/min per square meter, stroke volume index was 35.2 mL/m2, and total pulmonary resistance was 612.53 dyn. Ejection fraction was 27% by angiography. Maximal respiratory oxygen uptake was 6.0 mL/min by exercise testing. Biventricular pacing (BVP) was indicated to recoordinate ventricular contraction and resynchronize both ventricles in order to ameliorate the symptoms of heart failure. Additionally, implantable cardioverter defibrillator was indicated because of refractory ventricular tachyarrthythmia.
Preimplant test was performed to confirm operative indication. The procedure was performed while the patient was under general anesthesia. The right femoral vein was used for coronary sinus angiography. Anatomy of the coronary sinus system was presented. Optimal position of the left ventricular (LV) lead (target vein) was identified as the posterolateral vein. Indication for BVP was confirmed by an 18% increase in pulse pressure (PP) by stimulating both ventricles. Pulse pressure was calculated using the formula PP = peak systolic pressure–peak diastolic pressure.
Biventricular pacing implantation was performed under general anesthesia. The left subclavian vein was used for implantation. An LV pacing lead (Medtronic 2187, Medtronic Inc, Minneapolis, MN) was inserted into the identified target vein. Biventricular pacing was incorporated into the implantable cardioverter defibrillator pulse generator (Medtronic InSync implantable cardioverter defibrillator), providing both tachyarrythmia and heart failure therapies in a single device. The optimal pacing mode was biventricular stimulation with DDD sense and with an atrioventricular delay of 200 milliseconds. Sensed R wave amplitude of LV was 9.0 mV, stimulation impedance was 499 Ohm at 5.0 V, and pacing threshold was 0.7 V.
Echocardiography at 6 months after implantation showed that his ejection fraction had improved 23% to 36%. Although maximal respiratory oxygen uptake had improved 3 months after BVP implantation (12.0 mL/min) by exercise testing, it deteriorated 4 months after implantation (10.8 mL/min). Eight months after implantation, the patient was readmitted because of worsened dyspnea. There were no findings concerning coronary vascular accidents. Functional class was New York Heart Association class IV. Biventricular pacing was reexamined, and atrioventricular delay was changed to 220 milliseconds to optimize resynchronization. However, there was no clinical improvement. He was nominated as a candidate for heart transplantation and received a heart transplantation 232 days after implantation of BVP. The LV lead was located in the posterolateral vein. Ten months after the transplant he is doing well without significant complications.
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Desynchronization of both ventricles can cause an ineffective pattern of contraction in which segments of the heart contract at different times, which can cause contractile dysfunction and mitral regurgitation. Epidemiologic studies found that intraventricular conduction delay characterized by a discoordinate contraction pattern and wide QRS or by a bundle branch block is observed in about 30% of patients with congestive heart failure [1, 2].
Biventricular pacing may improve ventricular systolic and diastolic properties by the following mechanisms [1]: restortion of ventricular contractile synchrony [2], resynchronization of ventricular septal motion [3], pacing-induced decreases in atrioventricular valvular regurgitation [4], and pacing-related increases in ventricular diastolic filling time [3, 4]. If the patient has prolonged PR interval and wide QRS, these electromechanical abnormalities affect left atrioventricular synchrony and the ventricular contraction and relaxation sequence [5]. Ventricular resynchronization, either combined or not combined with atrioventricular synchrony optimization, should improve LV diastolic function by increasing filling time and atrial contribution, reducing the magnitude and duration of mitral regurgitation.
In our institute, BVP is indicated for drug-refractory congestive heart failure with New York Heart Association class III-IV, QRS duration more than 150 milliseconds, ejection fraction less than 35%, and LV end-diastolic dimension more than 60 mm. Biventricular pacing is indicated only for patients with more than 10% pulse pressure increase by preimplant test [6]. Patients recommended for heart transplantation may be included in our protocol.
Acute and chronic effects have been shown after BVP implantation [7, 8]. Shortly after implantation, hemodynamics improve. Auricchio and associates [7] demonstrated that BVP increased maximum LV dp/dt and pulse pressure. Improved symptoms and exercise tolerance have also been shown by long-term studies. Bakker and colleagues [8] demonstrated that median New York Heart Association functional class significantly improved 3 months after implantation. Results from noncontrolled studies have shown improvement of symptoms, exercise tolerance, and quality of life by BVP. Additionally, BVP with implantable cardioverter defibrillator prevents sudden cardiac deaths from ventricular tachyarrhythmia.
The BVP technique is currently in the evaluation process, and controlled, randomized trials will be necessary to validate this therapy to identify which patients respond better and to define more precisely its clinical relevance. Current bridging therapy, with ventricular assist devices, has significant risks of infection or neurologic complications. Biventricular pacing could become an effective bridge to heart transplantation or alternative to heart transplantation in patients with congestive heart failure and ventricular desynchronization.
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