Follow-Up. Cardiomyoplasty Comparison
Jorge Trainini, José Barisani, Jorge Mouras, Edmundo I. Cabrera Fischer, and Alejandra I. Christen
Presidente Perón Hospital, Avellaneda, Buenos Aires, Argentina
Abstract
Dynamic aortomyoplasty is an alternative technique to heart transplantation. The goal of our study was to evaluate the benefits of aortic counterpulsation obtained by dynamic aor- tomyoplasty in patients with heart failure refractory to pharmacological treatment and con- traindications to heart transplant or cardiomyoplasty.
In this study we compared preoperative and postoperative data of selected patients submit- ted who were treated with dynamic thoracic aortomyoplasty. This surgical technique wrap the right latissimus dorsi muscle flap around the ascending aorta. This muscle flap was electrically stimulated during diastole, following a muscle-conditioning protocol, to obtain diastolic augmentation. At twelve months follow-up period we evaluated, invasively and noninvasively, the hemodynamic and clinical effects of aortomyoplasty.
We observed a significant decrease in the number of hospitalizations (p<0.001), NYHA functional class (p<0.001), left atrial diameter (p<0.05), wedge pressure (p<0.05), left ven- tricular diameter (p<0.05) and pulmonary artery systolic pressure (p<0.05); and a significant increase in the 6-minute walking test (p<0.001), cardiac index (p<0.01), noninvasive eva- luation of diastolic augmentation (p=0.01), left ventricular shortening fraction (p<0.05), and radioisotopic left ventricular ejection fraction (p<0.05). We also found a non significant de- crease in peak oxygen consumption (p=0.05).
This nine patients operated with aortomyoplasty was compared with sixteen patients treated with cardiomyoplasty at twelve months of follow-up.
Dynamic biologic assistance with latissimus dorsi in heart failure, either aortomyoplasty or cardiomyoplasty in selected patients with severe heart failure, resulted in an important im- provement of hemodynamic parameters, heart functional data and clinical functional, without significant differences between the results of both techniques.
Key words: aortomyoplasty, cardiomyopathy, cardiomyoplasty, latissimus dorsi muscle, skeletal muscle.
Basic Appl Myol 10 (3): 119-125, 2000
C
ongestive heart failure is an important cause of morbility and mortality in the Western world. The treatment of severe heart failure has undergone several changes: administration of new drugs, cardiac trans- plantation and ventricular assist devices, resulting in a significative improvement in terms of quality of life and survival [22]. Nevertheless, an increasing number of pa- tients with cardiac diseases develop heart failure every year [12]. At present, several mechanical circulatory as- sistance devices are used as alternative treatments to provide bridge-to-transplant or even bridge-to-recovery for patients with severe heart failure refractory to phar- macological treatment.Chronic cardiac failure is not only a medical problem but also a social and economic concern, because many patients cannot benefit from cardiac transplant because organs need to come from healthy bodies; in addition, immunosuppression and scarcity of organ donors restrict this option [1].
Arterial counterpulsation has been used for treating acute severe left ventricular dysfunction in patients with refractory heart failure. Indeed, arterial counterpulsation using intra-aortic balloon pump has been widely used during the last 20 years in acute left ventricular failure.
Recently, patients suffering from refractory cardiac failure have been also treated with a biologic assistance
method called “dynamic aortomyoplasty” [7, 27]. This method consists in diastolic counterpulsation of as- cending or descending aorta through stimulation of latis- simus dorsi muscle flap wrapped around it. However, not very detailed clinical results or long term follow-up reports have been published, to the best of our knowl- edge [8, 26].
The goal of this study was to evaluate hemodynamic, functional and clinical effects of dynamic thoracic aor- tomyoplasty in a group of carefully selected patients with severe heart failure refractory to pharmacological treatment and contraindications for heart transplant or cardiomyoplasty.
Materials and Methods Population study
Nine patients (8 males) affected by severe chronic se- vere heart failure were referred to President Perón Hos- pital. Mean age was 55.4±7.4 years (69-44 years). All patients had previously had several episodes of acute pulmonary edema, despite the fact that all of them were under optimal medical therapy (low sodium diet, digi- talis, vasodilators, beta-blockers, angiotensin converting enzyme inhibitors and diuretics: furosemide and hidro- clorothiazide and/or amiloride and/or spironolactone).
In spite of this personalized therapy, these patients were admitted to hospital 4.0±1.6 times, during the year pre- vious to surgery, due to congestive heart failure. Dilated cardiomyopathy resulted from Chagas’ disease in 4 pa- tients, idiopathic dilated cardiomyopathy in 3 patients and coronary artery disease in 2 patients. Associated cardiac pathologies were: severe mitral regurgitation (n=6), moderate mitral regurgitation (n=3), severe tri- cuspid regurgitation (n=4) and mild tricuspid regurgita- tion (n=5). Aortic wall was explored with radioscopy and echographic studies and no calcifications were found in these patients. Pre-operative patient data in- cluded NYHA Class III in eight patients and Class IV in one patient. All patients were submitted to diagnostic coronary angiography and two showed severe stenotic lesions with no myocardium viability detected by radioi- sotopic ventriculogram and exercise thallium-201 scin- tigraphy. Left ventricular ejection fraction was assessed through radioisotopic studies. The aortomyoplasty pro- cedure was decided based on previously developed cri- teria (Table I).
All patients from this series had been rejected to car- diac transplantation due to aging (n=2), or Chagas’ dis- ease (n=4) or psycho-social factors (n=3).
Severe mitral regurgitation or cardiac enlargement ex- cluded these patients from dynamic cardiomyoplasty procedure. The preoperative hemodynamic and heart functional data of the patients are presents in Table II.
All data were obtained in compliance with protocols approved by the investigational review board of our in-
stitution. The patients were informed of the characteris- tics of the procedure and its risks and written consent was always obtained from each patient. During the whole period of therapy, all patients received psycho- logical assistance.
Surgical procedure
In all patients, a balloon-tipped catheter recorded the right atrium pressure, pulmonary pressures, wedge pres- sure and cardiac index. Afterwards, with the patient on left lateral decubitus, a wide cutaneous incision was made between the left axillary region and the posterior iliac crest. The right latissimus dorsi muscle was dis- sected and special care was taken to preserve its neuro- vascular bundle. Two pacing electrodes (Medtronic Table I. criteria for selection of patients.
Inclusion criteria
Dilated cardiomyopathy with heart failure NYHA III-IV.
Left ventricular ejection fraction < 30%
Peak VO2 < 20 ml/Kg/min
Contraindication for heart transplantation Contraindication for cardiomyoplasty Exclusion criteria
Aortic regurgitation Aortic calcification
Aortic aneurisma or dilatation >40 mm Refractory Hypertension (DBP > 90 mmHg) Arrhythmia refractory to drug treatment Neuromuscular disease
NYHA: New York Heart Association functional class, VO2: oxygen consumption, DBP: diastolic blood pressure.
Table II. Comparative analysis of pre-operative and 12- month post-operative data in patients after aorto- myoplasty.
Pre AMP Post AMP p NYHA Functional Class 3.1±0.4 1.1±0.4 <0.001 6 Minutes Walking Test (m) 394±84.6 525±97.5 <0.001 Peak VO2 (ml/Kg/min) 12.2±3.6 14.1±4.5 0.05 Cardiothoracic ratio 0.61±0.2 0.59±0.3 NS LV diastolic diameter (mm) 77.8±11.3 71.5±9.2 <0.05 LA diameter (mm) 56.5±5.6 48.2±11.3 <0.05 LV shortening Fraction (%) 13.2±5.3 18.7±6.4 <0.05 LV ejection fraction (%) 21.0±6.6 34.2±14.5 <0.05 PA systolic pressure (mmHg) 62.2±15.5 44.8±8.1 <0.05 Wedge pressure (mmHg) 28.2±6.7 20.5±8.3 <0.05 Cardiac index (L/min/m2) 2.0±0.3 2.65±0.44 <0.01 NYHA: New York Heart Association, VO2: peak oxygen consumption, LV: left ventricle, LA: left atrium, PA: pul- monary artery.
4750, Medtronic Inc., Minneapolis MN) were implanted into the proximal part of latissimus dorsi muscle. At this time, latissimus dorsi muscle flap was stimulated to de- termine its contractile response (threshold: 2V, resis- tance: 200Ω). An adequate contraction was obtained with an output of 3.5V. Then, the pedicled muscle flap was brought into the right chest after a 7cm resection of second right rib. After closure of this right incision a standard median sternotomy was performed and the as- cending aorta, aortic arch and collateral vessels were dissected. Once pericardium and right pleura were opened, the latissimus dorsi muscle flap was brought into mediastinum and its distal portion was wrapped around the ascending aorta in a counterclockwise fash- ion. The observed mean external aortic diameter was 3.5cm, the observed mean aortic length covered by latis- simus dorsi muscle flap was 6.0cm (from aortic root to brachiocephalic trunk) and two muscle layers were wrapped around the aorta.
Two sutureless epicardial leads (Medtronic 4755) were fixed to the right ventricle in order to sense the QRS of the electrocardiogram. A cardiomyostimulator (Medtronic, model 4710, Transform) was positioned in a left abdominal wall pocket. Both sensing and pacing leads were tunneled through subcutaneous tissue and connected to the cardiomyostimulator. In the last six pa- tients a minimal sternotomy (8cm) was performed. In these cases, a standard pacing lead was positioned in the right ventricle through superior cava vein.
Muscle stimulation protocol
Skeletal muscle flap electrostimulation started two weeks after surgery and a progressive muscle- conditioning protocol was followed, which was fulfilled in two months. This stimulation was similar to the one performed in cardiomyoplasty, but it took place during the diastole period of cardiac cycle.
Once the protocol was finished, stimulation started with the following characteristics: voltage: 3.5V, pulses per burst: 6, rate mode: 1:2 with heart rate, and synchro- nization delay: 230 to 490 milliseconds. The delay be- tween ventricular sensed contraction and muscle burst was adjusted through echocardiography to provide an exact synchronization between muscle flap contraction and ventricular diastole. The burst of pulses was trig- gered after aortic valve closure.
Patient follow-up
Once the progressive muscle-conditioning protocol was finished, 4 patients were submitted to aortic cinean- giographic studies in order to detect stenotic changes in aortic lumen. The aortic pressure curve and its temporal relationship with R wave of surface electrocardiogram also were recorded. The postoperative hemodynamic and heart functional data of these patients were obtained
at 12-month follow-up and they were compared with the corresponding pre-operative data.
The extent of diastolic aortic augmentation was meas- ures noninvasively by a counterpulsation index derived from diastolic and systolic areas beneath aortic pressure curve (DABAC/SABAC). To assess arterial pressure waves we used a technique for non-invasive beat-to-beat blood pressure monitoring in ambulatory patients. De- vices for clinical use are called Finapres (2300 Finapres, Ohmeda, CO, USA) or Portapres (Portapres Model-2, TNO-TPD Biomedical Instrumentation, Amsterdam, The Netherlands). This technique comprehends the Pe- naz volume-clamp approach combined with an infrared photoplethysmography that keeps volume of finger ar- tery at a preset value during testing time. Finapres rec- ords of finger artery pressure waves and surface electro- cardiogram were obtained in all patients during basal state. These signals were digitized in a compatible IBM PC computer. DABAC/SABAC index was calculated with on-line data acquisition of electrocardiogram and pressure signals, obtained with a Keithley DAS802 data acquisition board, driven by a specially written program in Visual Basic for Windows. Recording parameters were sampling frequency: 150 Hz, acquisition channels, 3; samples per acquisition, 800; and synchronism signal, taken from pulse generator. The DABAC/SABAC index was calculated through a program specifically developed in C++ language. This program was used on an IBM PC compatible computer.
The nine patients operated with aortomyoplasty was compared with sixteen patients treated with cardiomyo- plasty at 12 months of follow-up (Table III).
Calculations and statistical treatment
The DABAC/SABAC values were determined consid- ering the relationship between systolic area beneath the arterial pressure curve, enclosed between the dichrotic notch and the ascending foot of aortic pressure wave of the following cardiac cycle, and diastolic area beneath the arterial pressure waves, enclosed between the as- cending foot and the dichrotic notch of the aortic pres- sure curve. Values reported are expressed as mean±standard deviation. Statistical significance was assessed with paired Student’s t- test. A 95% confidence limit was chosen as indicator of statistical significance (p<0.05).
Results
There were no intraoperative or early post-operative deaths in this series. No in-hospital mortality was regis- tered, and the immediate post-operative course was un- eventful in general. Inotropic pharmacological support was routinely provided during 48 hours, and no intra- aortic counterpulsation was necessary in any case. All of the patients recovered from surgery was satisfactorily and each of them remained 5 days in the intensive care
unit. The post-operative hospitalization average was:
15.5±4 days.
Infection of surgical incision and cardiomyostimulator abdominal wall pocket developed in only one patient, and it was successfully treated with antibiotic therapy.
Two patients died at two and three months follow-up, due to ventricular arrhythmia, although they was re- ceiving medical therapy for severe ventricular arrhyth- mias and atrial fibrillation. Seven patients completed the muscle-conditioning period and they were followed during 18.1±10.7 months.
Four patients needed inotrope therapy one month be- fore aortomyoplasty. All patients received digoxine, enalapril and diuretics before surgery. Three patients were administered amiodarone before aortomyoplasty.
Two patients received oral anticoagulation and the other four patients were on aspirin before surgery. All patients received the same pharmacological treatment after aor- tomyoplasty. Diuretics doses were reduced in every pa- tient during the post-operative period.
At 12 month follow-up, clinical, hemodynamic and functional evaluation of these patients showed an im- provement in almost all parameters (Table II). Hospi- talizations due to congestive heart failure diminished from 4.0±1.6, during the year previous to aortomyo- plasty, to 0.4±0.7, during the first year after surgery (p<0.001).The noninvasive counterpulsation index (DABAC/SABAC) showed a significative increase be- tween assisted and non-assisted cardiac cycles (Table IV). Doppler echocardiography studies showed a de- crease in severity of mitral and tricuspid regurgitation in all surviving patients, if compared with the ones ob- tained previous to aortomyoplasty.
In four patients the aortic diastolic counterpulsation was observed with aortic cineangiographic studies. No thrombosis was found in ascending aorta and aortic valves were anatomically and functionally normal. No further alteration was observed in these invasive studies.
An invasive aortic pressure curve measurement was registered in each patient (Figure).
Discussion
Biologic aortic counterpulsation is a well-known tech- nique, introduced in 1958 by Kantrowitz [13]. Human application with intraaortic balloon pump results in beneficial hemodynamic effects, such as reduction of myocardial oxygen consumption, augmentation of coro- nary perfusion and increase of cardiac output [11, 14, 23]. Balloon counterpulsation can be used for short or intermediate term circulatory assistance. During the last decade, dynamic thoracic aortomyoplasty has been in- troduced as a new surgical technique to treat patients with severe heart failure. This is an attractive alternative because of the non-cardiac involvement of this surgical technique. Nature provides an example of chronic counterpulsation: diastolic augmentation is always ob- served in kangaroo’s aortic pressure signal [16]. Never- theless, not very detailed clinical results and long term Table III. comparative analysis of pre-operative and 12-month post-operative in patients after aortomyoplasty and cardio-
myoplasty.
Parameters AMP Preop AMP Postop CMP Preop CMP Postop
FC (NYHA) 3.1 ± 0.4 1.1 ± 0.4# 3.1 ± 0.3 1.7 ± 0.6*
Hospitalizations (nbr/p/yr) 4.0 ±1.6 0.4 ± 0.7# 2.0 ± 0.7& 0.4 ± 0.5*
LA Diameter (mm) 56.5 ± 5.6 48.2 ± 11.5 55.5 ± 10.0 53.2 ± 10.0
LV Diastolic Diameter (mm) 77.8 ± 11.3 71.5 ± 9.2 72.7 ± 7.0 72.3 ± 8.0
LV Shortening Fraction (%) 13.2 ± 5.3 18.7 ± 6.4# 15.6 ± 4.0 20.6 ± 5.0*
LV Ejection Fraction (%) 21.0 ± 6.6 34.2 ± 14.5# 23.6 ± 3.0 29.7 ± 5.0*
6 min Walking Test (m) 394 ± 85 525 ± 98 332 ± 127 421 ± 102
VO2 max (ml/Kg/sec) 12.2 ± 3.6 14.1 ± 4.5 13.3 ± 3.0 14.3 ± 3.0
References: AMP: aortomyoplasty; CMP: cardiomyoplasty; FC (NYHA): functional class (New York Heart Association); LA:
left atrial; LV: left ventricular; VO2: oxygen consumption.
p<0.05; # AMP Preop vs AMP Postop; * CMP Preop vs CMP Postop; & AMP Preop vs CMP Preop.
Table IV. Non invasive evaluation of diastolic augmenta- tion in aortomyoplasty.
NON-ASSISTED ASSISTED
Patient # 1 1.57 1.66
Patient # 2 2.03 2.33
Patient # 3 1.24 1.48
Patient # 4 1.13 1.33
Patient # 5 2.22 2.52
MEAN±SD 1.64±0.48 1.86±0.59∗
Diastolic augmentation evaluated through diastolic/systolic areas beneath the arterial pressure curve relationship in as- sisted and unassisted cardiac cycles. Assisted vs. non- assisted values show a significative increase of diastolic augmentation in patients submitted to aortomyoplasty pro- cedure.
∗ (p=0.01)
follow-up with clinical, hemodynamic and functional evaluations pre-operatively and post-operatively have been published.
Another series of surgical approaches to severe heart failure refractory to pharmacological treatment have been published. Mitral regurgitation is usually found in patients with severe left ventricle dysfunction and dila- tation. Bolling reported that patients with dilated car- diomyopathy and mitral regurgitation improved after mitral repair [4]. Aortomyoplasty also causes a reduc- tion in patients’ afterload, which improves mitral regur- gitation as Bolling technique does, with similar clinical results. The Batista procedure, consisting in partial left venticulectomy in dilated cardiomyopathy, still shows a high surgical mortality: 15%, and a poor life expectancy at twelve months follow-up: 56% [32].
Aortomyoplasty has been performed in ascending aorta and in descending thoracic aorta [2-3, 15]. We preferred ascending aorta to descending aorta in order to avoid the risk of paraplegia due to spinal chord ischae- mia. By using ascending aorta, we hoped to gain maxi- mal mechanical advantage of placing a counterpulsation as close as possible to pulse origin. Also, the diastolic augmentation of coronary blood flow is optimized. Fur- thermore, diameter of ascending aorta is larger than that of descending aorta.
The progressive muscle-conditioning protocol was de- signed to induce fast fatigue-resistant muscle with ad- vantageous biomechanical characteristics for the pur- poses of aortomyoplasty [18-21, 31]. The total stimula- tion threshold, the minimum voltage needed for a total
muscle contraction, was measured during surgical pro- cedure and it was never increased, as high voltage elec- tromyostimulation has been related to muscle fibrosis.
The stimulation rate was 1:2 with heart rate, to avoid overstimulation. Hemodynamic and doppler echocardi- ography studies demonstrated the diastolic augmentation and compression of aorta during latissimus dorsi muscle flap electrostimulation.
The latissimus dorsi muscle flap is usually used in car- diomyoplasty [6, 10]. Due to the enlargement of ven- tricular diameters in end stage heart failure, pericardial patches are sometimes necessary to obtain an optimal cardiac wrapping [9, 29]. Nevertheless, in aortomyo- plasty, total mass of skeletal muscle required to provide an adequate counterpulsation is largely provided by the latissimus dorsi and no supplementary patches are nec- essary. Aortic enlargement by means of a pericardial patch was not necessary in our patients, because the aortic root diameter was appropriate. Perhaps the vol- ume of skeletal muscle is an important factor in long- term integrity of pedicled flaps under electrical stimula- tion.
During follow-up, diuretics doses were reduced in every patient, and all of them used lower doses of their optimal pharmacologic treatment than they had used be- fore aortomyoplasty. We also observed a decrease in left atrium and right ventricular sizes, which was related to a decrease in systolic pulmonary artery pressure, and a decrease in cardiothoracic index. Doppler echocardi- ography showed a decrease in severity of mitral and tri- cuspid regurgitation. Left ventricle size, measured with echocardiography, showed a decrease, which could be considered a trend, similar to the one observed with car- diomyoplasty. We also found an increase in 6 minutes walking test results and in left ventricle shortening and ejection fractions. The increase observed in oxygen con- sumption test results was comparatively lower, perhaps due to peripheral mechanisms. A significative increase was found in non-invasive counterpulsation index values between assisted and non-assisted cardiac values. This objective technique, based on the Penaz principle, could be useful in evaluating long term evolution of chronic counterpulsation [5, 17]. On the other hand, the diastolic changes observed in the invasive records of aortic pres- sure signal (n=5) seemed minimal and no statistical studies were performed. The data supported that the procedure resulted in a decrease of the number of hos- pitalizations due to congestive heart failure.
In conclusion, dynamic thoracic aortomyoplasty seems to be an efficient technique to assist patients suffer from severe heart failure refractory to drug treatment and have contraindications for cardiomyoplasty or heart transplant. Our treatment of end-stage cardiac failure with aortomyoplasty in carefully selected patients re- Figure. Hemodynamic measurements during latissimus
dorsi muscle flap stimulation recorded in a pa- tient submitted to dynamic aortomyoplasty. The upper panel shows electrical stimuli (*) obtained by surface electrocardiogram (EKG); and in the lower panel, the corresponding aortic pressure wave (PAo) shows a diastolic augmentation during thoracic aortic counterpulsation.
sulted in an effective improvement of clinical, hemody- namic and heart functional parameters.
Current clinical evaluation shows an improvement of functional class and quality of life of those patients submitted to aortomyoplasty. A larger clinical experi- ence, a randomized study and a longer follow-up with periodic clinical controls and hemodynamic and func- tional evaluations would be useful to evaluate long-term effects of this technique in order to confirm its clinical relevance [24-25, 28, 30].
On the other hand dynamic biologic assistance with latissimus dorsi in heart failure, either aortomyoplasty or cardiomyoplasty in selected patients with severe heart failure, resulted in an important improvement of hemo- dynamic parameters, heart functional data and clinical functional class, without significant differences between the results of both techniques.
Address correspondence to:
Dr. Jorge Trainini, M.D., Brandsen 1690 - 3 A, (1287) Buenos Aires, Argentina. Phone and fax (54 11) 4302 3810, EMail alumni@ffinme.edu.ar.
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