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Ann Thorac Surg 2003;75:1205-1208
© 2003 The Society of Thoracic Surgeons

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Original article: cardiovascular

Ventricular energetics in endoventricular circular patch plasty for dyskinetic anterior left ventricular aneurysm

^a Cardiovascular Surgery, Aso-Iizuka Hospital, Iizuka, Japan

Accepted for publication November 6, 2002.

^* Address reprint requests to Dr Tanoue, Department of Cardiovascular Surgery, Aso-Iizuka Hospital, Yoshio-cho 3-83, Iizuka-city 820-8505, Japan.
e-mail: tanoue{at}heart.med.kyushu-u.ac.jp

	Abstract

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BACKGROUND: The endoventricular circular patch plasty (Dor procedure) applies to patients with a left ventricular dysfunction due to an ischemic dilated ventricle. In the present study, we analyzed left ventricular energetics in patients who underwent the Dor procedure.

METHODS: We measured left ventricular contractility (end-systolic elastance; Ees), afterload (effective arterial elastance; Ea), and efficiency (ventriculoarterial coupling; Ea/Ees, and the ratio of stroke work and pressure-volume area; SW/PVA) based on the cardiac catheterization data before and after the Dor procedure in 8 patients with a postinfarction dyskinetic anterior left ventricular aneurysm. Concomitant procedures included coronary artery bypass grafting in all patients, mitral valve repair in one patient, and cryoablation in one patient. End-systolic elastance (Ees) and Ea were approximated as follows: Ees = mean arterial pressure/minimal left ventricular volume, and Ea = maximal left ventricular pressure/(maximal left ventricular volume–minimal left ventricular volume), and thereafter Ea/Ees and SW/PVA were calculated. The left ventricular volume was normalized with the body surface area.

RESULTS: End-systolic elastance (Ees) increased after the Dor procedure (from 1.15 ± 0.60 to 1.86 ± 0.84 mm Hg · m² · mL^-1, p < 0.01), thus resulting in an improvement in Ea/Ees and SW/PVA (from 2.94 ± 1.11 to 1.64 ± 0.49, p < 0.01, and from 0.426 ± 0.110 to 0.559 ± 0.082, p < 0.01, respectively), even though Ea did not substantially change (from 2.96 ± 0.78 to 2.74 ± 0.55 mm Hg · m² · mL^-1, p = 0.4).

CONCLUSIONS: Left ventricular contractility and efficiency improves after the Dor procedure in patients with a dyskinetic anterior left ventricular aneurysm. However, afterload does not change. The use of appropriate afterload-reducing therapy thus plays an especially important role in the management of patients who undergo the Dor procedure.

	Introduction

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Ventricular volume reduction surgery for an ischemic dilated left ventricle has recently become an interesting new field for cardiac surgeons. Endoventricular circular patch plasty (Dor procedure) has been reported to be a surgical method that applies to patients with a left ventricular (LV) dysfunction after a myocardial infarction for either akinesia or dyskinesia [1]. In this procedure, the LV volume is reduced and the LV chamber is reconstructed using an endoventricular circular patch. Multicenter clinical studies have reported the Dor procedure to be a safe and effective operation in the treatment of the remodeled dilated left ventricle after an anterior myocardial infarction [2].

The concept of end-systolic elastance (Ees), effective arterial elastance (Ea), and ventriculoarterial coupling (Ea/Ees) provides a useful framework for analyzing the interplay between contractility and afterload [3, 4]. We previously reported the approximation of Ees, Ea, and Ea/Ees using a canine right-heart-bypass preparation with a conductance catheter in the LV cavity, and then compared the cardiac performance of the patients treated by a total cavopulmonary connection [5]. Using this approximation, we analyzed left ventricular energetics based on the cardiac catheterization data before and after the Dor procedure in patients with a postinfarction dyskinetic anterior LV aneurysm in the present study.

	Material and methods

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Patient information
From December 1994 to March 2002, 11 consecutive patients with postinfarction dyskinetic anterior LV aneurysms electively underwent the Dor procedure at the Aso-Iizuka Hospital. Eight patients, consisting of 4 males and 4 females, were retrospectively selected for this study because left ventriculography could not be performed in the other three patients due to severe renal dysfunction. Informed consent for both the operation and cardiac catheterization was obtained from all patients. The mean age of the studied patients was 61.5 ± 13.5 years (36 to 77 years) and the mean weight was 61.8 ± 10.1 kg (47 to 75 kg). New York Heart Association functional grade was II in 3 patients and III in 5 patients.

Operative techniques
The operations were performed by 2 cardiac surgeons (H.A. and J.T.). Anesthesia was done by the standard intravenous technique with fentanyl, midazolam, and pancuronium for muscle relaxation. Aortic and bicaval or right appendage cannulations were performed thorough a standard median sternotomy, and cardiopulmonary bypass was instituted with a heart-lung machine consisting of a centrifugal pump and a membrane oxygenator. The procedure was performed under total cardiac arrest with anterograde and retrograde cold blood cardioplegia. Coronary revascularization was first performed, and then the Dor procedure [1, 2]. The left ventricle was opened at the center of the scar, and if necessary, cryoablation was performed. An encircling 2–0 braided suture was passed around the endocardial fibrous scar, and a hemicircular patch was anchored to the fibrotic tissue to close the orifice and reconstruct the LV internal cavity. The LV incision was closed with pledgeted sutures. Regarding concomitant procedures, coronary artery bypass grafting (CABG) was performed in all patients; mitral valve repair was performed in one patient; and cryoablation was performed in one patient.

Data analysis
All patients underwent cardiac catheterization both before and about 3 to 4 weeks after the operation. Biplane left ventriculography was performed, and the LV volume was calculated by the area-length method [6]. Left ventricular (LV) end-diastolic volume index (EDVI), end-systolic volume index (ESVI) and ejection fraction (EF) were calculated. The calculations of Ees (contractility), Ea (afterload), and Ea/Ees (ventricular efficiency) were performed based on the pressure and volume data of cardiac catheterization by an approximation method as previously described [5]. The approximation of Ees and Ea were performed as follows: Ees = mean arterial pressure/minimal LV volume, and Ea = maximal LV pressure/(maximal LV volume - minimal LV volume). The LV volume was normalized with the body surface area. The ratio of Ea to Ees (Ea/Ees) and the ratio of stroke work and pressure-volume area (SW/PVA) were calculated as indices of ventricular efficiency. Ea/Ees is ventriculoarterial coupling between the left ventricle and the arterial system described by Burkhoff [4]. Stroke work and pressure-volume area (SW/PVA) was calculated as follows: SW/PVA = 1/(1 + 0.5Ea/Ees). This theoretical formula was described by Nozawa [7].

Statistical analysis
The results are presented as mean±SD. Student’s paired t test was used to compare the changes in the values before and after operation.

	Results

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There was no perioperative and hospital death. The mean cardiopulmonary bypass time was 214.6 ± 27.7 minutes while the mean aortic cross-clamp time was 158.6 ± 34.4 minutes. The mean number of bypass grafts was 2.4 ± 1.2. Dyskinetic LV aneurysm disappeared in all patients and grafts were all patent on postoperative cardiac catheterization.

Heart rate, pulmonary capillary wedge pressure, mean blood pressure, and cardiac index are shown in Table 1. No significant difference was observed before and after operation regarding these conventional hemodynamic variables.

View larger version (24K): [in this window] [in a new window]   Fig 1. Left ventricular volume indices before and after operation. (A) EDVI and (B) ESVI decreased and (C) EF improved after the Dor procedure. Black circles and solid lines indicate values of each patient. Open circles indicate mean values of all patients, and bars indicate SD. (EDVI = end-diastolic volume index; EF = ejection fraction; ESVI = end-systolic volume index.)

View larger version (29K): [in this window] [in a new window]   Fig 2. Left ventricular efficiency before and after operation. (A) Ees increased after the Dor procedure, thus resulting in an improvement in (C) Ea/Ees and (D) SW/PVA, even though (B) Ea did not substantially change. Black circles and solid lines indicate values of each patient. Open circles indicate mean values of all patients, and bars indicate SD. (Ea = effective arterial elastance; Ea/Ees = ventriculoarterial coupling; Ees = end-systolic elastance; SW/PVA = the ratio of stroke work and pressure-volume area.)

	Comment

Top Abstract Introduction Material and methods Results Comment References

Ventricular volume reduction surgery for a dilated left ventricle is a relatively new surgical field. The Dor procedure has been reported to improve both EF and New York Heart Association function class in patients with either anterior akinetic scar or dyskinetic aneurysm and depressed LV function [2, 8, 9]. This infarct exclusion repair using a circular patch both reduces ventricular wall stress (Laplace’s law) and transforms the spherical ventricle to a more normal elliptical shape [9]. Laplace’s law is often cited as the physiologic principle underlying the benefits of volume reduction surgery. However, the reconstruction of LV geometry is considered to be as important as a reduction of the LV wall stress due to the complicated movements of the left ventricle. Left ventricular (LV) volume reduction achieved through removing dyskinetic anterior LV aneurysm is considered to very effectively reduce LV wall stress. The LV geometry reconstruction performed by obviating the LV aneurysm is also considered to be a very effective procedure. We performed the Dor procedure in patients with dyskinetic anterior LV aneurysms and not in those with akinetic LV scar.

It is difficult to assess the effects of LV volume reduction by measuring ordinary hemodynamic variables alone. In the present study, conventional hemodynamic variables (heart rate, pulmonary capillary wedge pressure, mean blood pressure, and cardiac index) did not change after the Dor procedure. In contrast, the load-independent parameters of systolic ventricular function, Ees, increased significantly after the Dor procedure. As a result, the index of ventricular efficiency, Ea/Ees improved after the operation, although the parameter of afterload, Ea, did not change. The approximation of Ees and Ea in this study inherently has limitations and does not amount to the measurement by conductance catheter, and the volume intercept could not be measured. However, the present approximation enables us to evaluate ventricular contractility, afterload, and ventriculoarterial coupling from the conventional cardiac catheterization data [5]. This promising approximation is also considered to be useful for other clinical cases.

Ventriculoarterial coupling has been studied in patients who underwent the Dor procedure by Fantini and colleagues [10]. They reported that ventriculoarterial coupling improved after the Dor procedure because of the decrease in Ea. In the present study, the improvement of ventriculoarterial coupling after the Dor procedure was mainly due to the increase in Ees, while Ea did not change. This discrepancy is attributable to not only the different methods in analysis but also patient selection. The Dor procedure is only performed in selected patients with dyskinetic anterior LV aneurysms in our hospital. However, an improvement of ventriculoarterial coupling after the Dor procedure was demonstrated in both clinical studies.

The Dor procedure for patients with an akinetic scar of the LV wall was reported to be the effective operation [2, 8, 9]. However, there is still less of a consensus regarding the volume reduction through exclusion of an akinetic LV wall segment [11, 12]. Recently, Atrip and colleagues reported that a resection of a dyskinetic segment increases the overall pump function, but a resection of an akinetic section has little effect, using a theoretical model [13]. We thus speculate that the improvement of ventricular efficiency after the Dor procedure in patients with an akinetic LV scar is not as significant as in patients with a dyskinetic LV aneurysm. In our hospital, the Dor procedure is not performed in patients with an akinetic LV wall, but in patients with a dyskinetic LV wall (aneurysm). Coronary artery bypass grafting (without cardiopulmonary bypass, if possible) is only performed in patients with an akinetic LV wall and congestive heart failure.

We demonstrated that Ea did not improve after the Dor procedure. In our hospital, olprinone (phosphodiesterase III Inhibitor) infusion is performed while patients are weaned from cardiopulmonary bypass and also in the early postoperative period. We reported the preload and afterload-reducing effect of olprinone combined with the positive inotropic effect using a canine right heart bypass model [14]. The use of phosphodiesterase III Inhibitor is strongly recommended during the perioperative period after the Dor procedure. Because not only the short-term usage, but also the long-term appropriate usage of vasodilatory agents both play an important role in the therapeutic strategy for patients after the Dor procedure, angiotensin converting enzyme inhibitor, angiotensin II receptor blocker and/or ß-blocker are administered long-term after oral intake is established. This medication is considered to decrease afterload, correct an afterload mismatch, and improve ventricular efficiency, thereby improving the long-term outcome.

The improvement in contractility may be due both to the Dor procedure and to the concomitant CABG [15]. It is difficult to evaluate the pure effect of the Dor procedure on cardiac performance, because CABG was always performed at the same time. However, two patients in this study only underwent bypass grafting to the left anterior descending coronary artery, and their Ees improved after the operation. The improvement in Ees after operation was due to synergistic effects. Finally, we only studied the clinical effect of the Dor procedure on patients with dyskinetic anterior LV aneurysm. Further studies evaluating the effect of the Dor procedure on patients with an akinetic LV scar are thus called for.

In conclusion, both LV contractility and efficiency improve after the Dor procedure in patients with dyskinetic anterior LV aneurysms. However, afterload does not change. Appropriate afterload-reducing therapy is therefore considered to play an important role in the management of patients who undergo the Dor procedure.

	References

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