Keywords
INTRODUCTION
The diagnostic-therapeutic strategy for patients with persistent ventricular arrhythmias associated with chronic myocardial infarction include the study of coronary artery anatomy, ventricular function, and programmed electrical stimulation to test the reproducibility of the arrhythmia and its possible source. Cardiac revascularization is the treatment of choice in the presence of residual ischemia. Nevertheless, the efficacy of cardiac revascularization in controlling ventricular arrhythmias is unclear.1-4 In the presence of ventricular arrhythmia, aneurysmectomy in conjunction with endocardial resection has resulted in greater success rates for controlling ventricular arrythmias.5,6
In this study, we performed a prospective follow-up study of our clinical interventions that included coronary revascularization, resection of the aneurysm or the implantation of an automatic defibrillator (AID), or both, in patients with ventricular arrhythmias and chronic myocardial infarction.
PATIENTS AND METHOD
Between June, 1995, and September, 2001, we studied 53 patients with ventricular arrhythmias in our cardiac electrophysiological laboratory at the Hospital Universitario Virgen Macarena de Sevilla. Of these 53 patients, 17 had heart disease with ventricular aneurysm secondary to interventionist treatment. A total of 15 patients had a history of myocardial infarction, but all patients presented with symptoms of hypokinesia, akinesia, or dyskinesia, or all three. We excluded from the study those patients with evidence of acute ischemia associated with the arrhythmic event and divided the patients into 2 groups: those who had a left ventricular aneurysm (group 1) and those who did not (group 2).
Coronary angiography
Coronary angiography was performed in accordance with standard procedures between 5 and 30 days after the episode of arrhythmia.
Coronary revascularization
The indication for performing coronary revascularization was established according to the severity of the lesions on coronary angiogram and after evaluating the existence of residual ischemia.
Surgical procedure for ventricular aneurysms
Surgical procedures were performed using the Jatene and Cooley endoaneurysmorrhaphy technique,7 with surgical endocardial resection of the edges of the fibrous scar. The criteria for resection were exclusively technical, and the surgical team evaluated whether the resection was physically possible, taking into account anatomical features as seen on contrast ventriculography.
Electrophysiological study
Electrophysiological study was performed using two quadripolar 6 Fr electrocatheters for recording and stimulation. The stimulation protocol at the apex of the right ventricle used 1 to 3 premature extra stimuli during the sinus rhythm and during 3 cycle longitudes (600, 500, and 400 ms) of stimulation with a ventricular pacemaker. The arrhythmia induction test was considered positive if it induced ventricular tachycardia that was sustained for more than 30 seconds or if it was poorly tolerated hemodynamically, requiring electrical cardioversion to stop it.
Follow-up
During follow-up, recurrent arrhythmia was considered to be present after documentation of the existence of sustained ventricular arrhythmia on electrocardiograph or recording results from the defibrillator electrogram, and in the presence of sudden cardiac death. Follow-up was performed by direct contact in the outpatient clinic or by telephone interview.
Statistical analysis
The qualitative variables were compared by means of the exact Fisher test. The quantitative variables were expressed as mean and standard deviation (SD) and analyzed by the Student t test.
RESULTS
Baseline clinical characteristics of the patient sample are shown in Table 1. All but 1 patient presented with significant cardiac lesions (stenosis ≥50%). That patient had a history of traumatic myocardial infarct at the age of 4 years, and at the age of 24 years presented with sustained monomorphic ventricular tachycardia (SMVT), evident by the presence of an apical aneurysm on ventriculography. One patient with a ventricular aneurysm did not agree to repeat coronary angiography and provided the record from a coronary angiography exam performed 5 years previously, which revealed occlusion of the anterior descending artery. A total of 12 patients had an aneurysm in the left ventricle, 11 in the anterior location and one in the posterobasal location. The mean ejection fraction was 32% (SD, 9.93). The spontaneous ventricular arrhythmia was an SMVT in 12 patients, ventricular fibrillation (VF) in 4 patients, and 1 patient presented with characteristics of the MADIT type (non-sustained ventricular tachycardia, EF<35%, and inducible SMVT). The episode of arrhythmia occurred between 7 days and 20 years after the myocardial infarct (mean, 39 months; SD, 62.77).
Coronary revascularization and aneurysmectomy (Table 2)
Of the 12 patients with a left ventricular aneurysm (group 1), 7 underwent an endoaneurysmorrhaphy with the Jatene technique accompanied by endocardial resection; 4 of these patients also underwent revascularization. In 2 patients with aneurysm it was only possible to perform coronary revascularization. There were 3 patients whose aneurysms could not be resected and who could not undergo coronary revascularization. All the patients in group 2 (5 cases without aneurysm) underwent revascularization. Therefore, among both groups there were 7 patients who only underwent revascularization and 14 who underwent some type of intervention.
Electrophysiological study (Table 3)
A pre-intervention electrophysiological study (EPS) was performed in only 5 patients? in 3 patients because they had not undergone an intervention of any type, in another patient because the study was negative and was obviously not going to change after the intervention, and in the fifth patient who was diagnosed post-operatively with an advanced gastric neoplasm after the aneurysmectomy who rejected the post-intervention EPS. In 6 patients the post-intervention EPS was not performed because of logistical problems and in opposition to our wishes. In any case, the fact that arrhythmias could be induced in 4 patients following revascularization and not induced in 2 patients following aneurysmectomy allowed us to adjust the AID appropriately. The remaining 6 patients underwent pre- and post-intervention EPS.
Clinical recurrence of ventricular arrhythmias (Table 4)
A total of 15 patients were followed for more than 1 year, and 1 patient was followed for 6 months; in addition, one of the patients who underwent intervention for an aneurysm died 2 months after the procedure of noncardiac-related causes (hemorrhagic shock due to gastric neoplasm). Mean follow-up was 33.64 months (2 to 72 months). During this entire period, 6 patients had a recurrence of sustained ventricular arrhythmia (3 of the SMVT type and 3 of the VF type; 3 patients belonged to group 2 and 3 to group 2). The 3 recurrences in group 1 corresponded to patients whose aneurysms had not been resected (P<.05). With regard to the patients who only underwent revascularization (2 in group 1 and 5 in group 2), the recurrence rate was 57%. The time interval between the initial episode of arrhythmia and the recurrent episode varied from 1 to 5 months.
Implantation of an automatic implantable defibrillator (AID) (Tables 3 and 5)
The decision as to whether or not an AID should be implanted was influenced by: whether the spontaneous ventricular arrhythmia was of the VF type, whether the patient could undergo an intervention or not, and the result of the post-intervention EPS. There was no indication for an AID in 6 patients, all of whom had undergone aneurysmectomy. In 5 of these patients, post-intervention EPS was negative. The 6th patient, diagnosed with advanced gastric neoplasm postoperatively, was not subjected to a second EPS as the patient´s spontaneous arrhythmia was not of the VF type. None of these 6 patients had a recurrence of arrhythmia. In the remaining 11 patients, the implantation of an AID was indicated: in 3 because they did not undergo intervention and presented with a positive baseline EPS; in 7 patients because the post-intervention EPS was positive, and in 1 patient because the pre-intervention EPS was negative (revascularization) and the spontaneous arrhythmia was of the VF type.
Anti-arrhythmia treatment in follow-up
An anti-arrhythmia medication was prescribed (sotalol, amiodarone, carvedilol, or atenolol) for 14 patients: for 9 patients in group 1 and 5 in group 2. In group 1, 4 of the 7 patients whose aneurysm was resected received anti-arrhythmia medication and the 5 patients who did not undergo intervention for the aneurysm received anti-arrhythmia medication.
DISCUSSION
We attempted to study a group of patients with sustained ventricular arrhythmia associated with a chronic myocardial infarct who presented with heart disease or ventricular aneurysm, or both, after revascularization or aneurysmectomy. Our aim was to determine if these interventions influenced the recurrence of arrhythmias.
In actuality, the number of interventions for ventricular aneurysms due to arrhythmias has is decreased due to the implantation of automatic defibrillators. Nevertheless, the complete management of these patients with resection of the aneurysm, ablation of the arrhythmiagenic focus, and coronary revascularization, would appear to be the best intervention. It has actually been possible to simplify these procedures, particularly with use of intraoperative mapping. Some authors6,8,9 have shown that aneurysmectomy with endocardial resection of the edges of the fibrous scar without intraoperative mapping achieves results similar to those obtained by using mapping. In our study, the success rate for avoiding the recurrence of arrhythmias was complete, and the arrhythmia stopped being reproducible in 5 of the 6 patients in whom post-surgical EPS was performed. This was not the case in those patients whose aneurysms were not resected, and a recurrence of arrhythmias occurred in 3 of these 5 patients (P<.05). Frapier et al,6 after performing endocardial resection with cryoablation without using intraoperative mapping, achieved an 89% lack of recurrence of arrhythmias and they could no longer induce arrhythmias in 94.5% of their patients.
The influence of coronary revascularization for controlling ventricular arrhythmia in patients with chronic myocardial infarcts is uncertain. When it can be determined that acute ischemia is the trigger for the arrhythmia (principally polymorphic or VF ventricular tachycardia), revascularization has proven to be useful.3,4 Nevertheless, in the majority of cases, it is difficult to prove the source of the ischemic trigger. We were able to prove in our study that there is a high recurrence rate of arrhythmias (57%) in those patients who only undergo revascularization, and that their arrhythmias are inducible after the revascularization. Therefore, the substrate of the arrhythmia is scarcely modified by this intervention. A similar conclusion was reached by Brugada et al10 and others.1
It is of note that the majority of our patients received anti-arrhythmia agents during follow-up, which may have skewed our results.
Of the 2 factors that can originate ventricular arrhythmias associated with chronic myocardial infarction, with scarring and ischemia as contributing factors, scarring is probably the most important. Resection of the scar, therefore, should be performed whenever possible, particularly when an aneurysm is present. In cases of infarct without aneurysm, endocardial ablation of the arrhythmia substrate is limited by the necessity of maintaining the patient on TV during the study, although there have been reports of attempts to perform this during sinus rhythm.11 This method, combined with coronary revascularization and the appropriate anti-arrhythmia therapy, may allow us to save some of our patients from the disagreeable experience of AID electric shocks.
CONCLUSIONS
Aneurysmectomy with endocardial resection constitutes, in our experience, an efficient tool for controlling ventricular arrhythmias associated with aneurysms of the left ventricle.
Coronary revascularization in patients with ventricular arrhythmias and chronic myocardial infarction do not appear to influence the prevention of the recurrence of arrhythmias.
Correspondence: Dr. A. Felices Nieto.
Luis Fuentes Bejarano, 3, casa 75. 41020 Sevilla. Spain
E-mail: afelices@wanadoo.es