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Eur J Cardiothorac Surg 2002;22:762-770
© 2002 Elsevier Science NL
a Department of Cardiothoracic Surgery, Cardiac Directorate, University Hospital of Wales, Cardiff, CF14 4XW, UK
b Vincent Pallotti Hospital, Cape Town, South Africa
c Cardiac Clinic, Department of Medicine, University of Cape Town, Cape Town, South Africa
Received 11 February 2002; received in revised form 6 August 2002; accepted 8 August 2002.
* Corresponding author. Tel.: +44-29-2074-2944; fax: +44-29-2074-5439
e-mail: uvonopp{at}uhw-tr.wales.nhs.uk
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Abstract |
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 Top Abstract 1. Introduction2. Methods3. Results4. Discussion5. ConclusionReferences |
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Key Words: Arrhythmia • Ventricular tachycardia • Treatment • Surgery • Endocardial resection • Cryoablation
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1. Introduction |
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TopAbstract1. Introduction2. Methods3. Results4. Discussion5. ConclusionReferences |
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The automatic implantable cardioverter defibrillator (ICD) has proven to be an effective palliative device for the detection and immediate treatment of life-threatening tachyarrhythmias [2]. Implantation is associated with a low (less than 3%) operative mortality, and the diagnostic accuracy of the device is excellent. However, the ICD does not prevent arrhythmias, and the majority of patients still require antiarrhythmic medication. In addition, the device discharge is unpleasant and impractical in patients with frequent tachyarrhythmias. Associated left ventricular (LV) dysfunction is a negative predictor of long-term survival [3], and LV function is unaltered by device implantation. Surgery on the other hand offers a potentially curative therapy for VT as well as a means of improving LV function through ventricular remodelling of aneurysmal ventricles.
‘Indirect’ surgical procedures such as thoracic sympathectomy, coronary artery bypass grafting or simple LV aneurysmectomy alone have been used previously to treat refractory ischaemic ventricular arrhythmias. However, the operative mortality associated with these ‘indirect’ procedures has been high, and with successful cure of the arrhythmia in less than 25% of cases. Coronary revascularization in patients with ischaemic heart disease and VT, although improving the blood supply to ischaemic myocardium, rarely alters the arrhythmogenic potential of the myocardium. Furthermore, intraoperative electrophysiologic mapping has shown that the arrhythmogenic focus is not contained in tissue routinely excised at aneurysmectomy. Ventricular tachyarrhythmias, that occur after the initial 72 h of an acute myocardial infarction, originate from micro reentrant circuits in the peri-infarcted areas of abnormal but viable myocardial tissue in the endocardium and subendocardium. Consequently, the modern principle of surgical therapy involves the isolation or excision of scar tissue shown to be arrhythmogenic, as well as revascularization and LV aneurysmectomy with remodelling when indicated.
Endocardial resection procedures involve the excision of endocardial scar tissue with the aid of electrophysiologic guided mapping, and are also now frequently combined with cryoablation of mapped ectopic foci. If intraoperative mapping cannot be performed or VT is not inducible intraoperatively, then an extended endocardial resection of all visible scars is advised [4–6]. Intraoperative map guided procedures have been associated with operative mortalities of less than 10% [4,7–10] and successful cure of VT in more than 80% of patients [6,8,9,11].
In this study we review our surgical results of the treatment of VT of LV origin associated with either coronary artery disease or non-ischaemic idiopathic LV aneurysms.
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2. Methods |
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TopAbstract1. Introduction2. Methods3. Results4. Discussion5. ConclusionReferences |
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2.1. Surgical technique
All patients underwent preoperative electrophysiologic stimulation (EPS) and mapping in the cardiac catheterization laboratory, unless the risks were assessed as being too high (five patients) in which case EPS was only done intraoperatively with the availability of cardiopulmonary bypass. Early in this experience intraoperative mapping was performed with a customized patch containing 24 bipolar electrodes and analyzed manually (Midas, E for M Corporation/Helige, Freiburg, Germany). Currently, a linear catheter containing ten bipolar electrodes that is placed sequentially on different areas of the heart in conjunction with on screen cursors and more immediate analysis (Prucka Cardiolab, GE Marquette Medical systems, Milwaukee, WI) is now being used.
The operation was performed through a median sternotomy. Intraoperative EPS and epicardial mapping was performed on all patients, after cannulation for cardiopulmonary bypass (venous drainage via a single dual stage right atrial cannula and ascending aortic cannulation for arterial return). Thereafter on normothermic cardiopulmonary bypass the heart was fibrillated, a LV vent was inserted via the right superior pulmonary vein and the LV opened through the aneurysm or infarcted area. The heart was then defibrillated and an extended endocardial resection of all visible scar tissue was routinely performed, on the warm beating heart. Cryoablation lesions (nitrous oxide (N2O) was used as the cryogen which produces a probe temperature of approximately -65 °C; 10 mm diameter probe tip applied for 2 min) were applied liberally to transitional areas containing residual patchy fibrosis interspersed in the myocardium, especially to the base of papillary muscles if involved as well as to mapped foci. Further EPS was done after the endocardial resection, and any induced VT foci were mapped and cryoablated until VT could no longer be induced.
The junction of contracting myocardium was then identified by palpation and a ‘purse string’ suture of 3/0 polypropylene was inserted to geometrically remodel the LV [12]. Thereafter the ventriculotomy was closed by direct suture if the residual defect was small, or by means of a patch (bovine pericardium or Dacron). The Dor endoaneurysmorrhaphy technique was used preferentially [13], usually requiring a patch of approximately 2–3x3–4 cm in size. In two patients an epicardial patch was used with a ‘sandwich’ technique because of soft friable adjacent myocardium 3–4 weeks following an acute myocardial infarction.
Moderate systemic hypothermia (28–30 °C), aortic cross-clamping, combined antegrade/retrograde multidose cardioplegia with either cold oxygenated crystalloid (St. Thomas No. 2) or 1:1 cold blood cardioplegia, using the St. Thomas solution after the initial arresting dose, as well as intermittent topical 4 °C cooling were then used for coronary artery bypass grafting of all significant coronary stenoses. The left anterior descending coronary artery was grafted despite the presence of an anterior LV aneurysm if indicated, and preferentially with the left internal mammary artery.
Prior to discharge a further EPS was performed in the cardiac catheterization laboratory in 20 patients.
2.2. Follow-up
Patient data were collected prospectively, and follow-up was obtained from clinical records, referring hospital records and telephonic interviews if necessary. Operative mortality was defined as either 30-day or in-hospital mortality. The time interval required for complete follow-up was 6 months (prior to May 2001). Follow-up was complete in 100% of patients, and total follow-up was 98 patient years with an average follow-up of 3.8±3.1 years/patient (range 1 month to 9.9 years).
2.3. Statistics
Averages with standard deviations are provided. Statistical comparisons were by Fisher exact, independent or paired t-test, and log rank test (SPSS 11.0 Chicago, IL) as indicated. Survival curves with standard errors were by the Kaplan–Meier technique (GraphPad Prism 3.03, San Diego, CA). Significance was accepted as P<0.05.
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3. Results |
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TopAbstract1. Introduction2. Methods3. Results4. Discussion5. ConclusionReferences |
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Patients were grouped into 24 patients with ischaemic VT and two patients with VT associated with an idiopathic apical LV aneurysm and normal coronary arteries (non-ischaemic VT), as previously described.
3.1. Non-ischaemic VT
This small group of patients were younger (P=0.03), in a lower New York Heart Association (NYHA) functional class (P=0.03) and had better preoperative LV function (P=0.001) compared to the ischaemic VT group of patients (Table 1). The VT arrhythmic focus was mapped to idiopathic antero-apical LV aneurysms associated with normal coronary arteries in both patients. One patient had also presented with a cerebrovascular accident, presumed to have been embolic as a result of a clot contained in the LV aneurysm. Surgery successfully cured the VT in both patients, with no operative mortality or morbidity. The postoperative LV ejection fractions were no different to the preoperative values, and there has been no recurrence of VT during follow-up (average follow-up 3.0 years).
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More than one VT morphology was recorded in 33% of patients either pre- or intraoperatively. EPS was not done preoperatively in five patients because of perceived coronary anatomy risk, and all five of these patients were inducible at operation. One patient was not inducible pre- or intraoperatively, and an additional four patients who were inducible preoperatively were not inducible at the time of surgery. Preoperatively VT was induced in 95% of cases attempted, and intraoperatively VT was induced in 79% of cases (P=NS). Intraoperative EPS was also used to guide the extent of additional cryoablation.
Operative mortality was 8.3% (ischaemic VT patients), and on univariate analysis could be related to performing concomitant mitral or tricuspid valve repair surgery (P=0.02), and the need for perioperative intra-aortic balloon counterpulsation (P=0.02; Table 2). One operative death was related to the presence of preoperative sepsis in a patient requiring emergent surgery for life-threatening VT, and the other was due to cardiac failure. Mortality was not related to preoperative history of angina or congestive cardiac failure, angina class or extent of coronary disease, possibly because of the small size of this series. Morbidity included the need for an intra-aortic balloon pump (IABP) to wean from cardiopulmonary bypass in three patients (an additional patient had an IABP inserted preoperatively in an attempt to control incessant VT), and prolonged postoperative ventilation (more than 24 h) in 29% of patients (Table 1).
The left ventriculotomy was repaired according to the principles of Jatene [12], and then closed either by direct suture or Dor endoaneurysmorrhaphy in 92% of patients [13]. The average postoperative LV ejection fraction improved to 43.2±8.2% (P=0.0001 vs. preoperative ejection fraction), an individual increase of between 0 and 258%, and average percentage improvement of 72.4±67% of preoperative LV ejection fraction.
Postoperative EPS induced VT in one patient and on follow-up VT recurred in another three patients; VT surgical ‘failure’ (either recurrence or ability to induce VT postoperatively) was evident in 18% of ischaemic VT operative survivors. However, the recurrent VT in all of these previously medically refractory patients was now easily controlled with amiodarone antiarrhythmic medication. Risk factors for VT surgical ‘failure’ included patients with a mapped arrhythmic focus remote to the LV aneurysm/ventriculotomy (P=0.015), and if only cryoablation or endocardial resection alone (as opposed to in combination) had been performed (P=0.003; Table 2). Cryoablation alone had been performed if there was no visible resectable endocardial scar, and therefore a presumed intramural as opposed to endocardial focus. We observed a tendency for a higher incidence of VT recurrence in patients with no true LV aneurysms and inferior located aneurysms (P=0.08; Table 2).
Freedom from VT recurrence/surgical ‘failure’ in operative survivors was 85.3±7.9%, 78.8±9.6%, and 78.8±9.6% at 2, 5 and 10 years, respectively (Fig. 1) . There was a tendency towards a lower freedom from VT recurrence or postoperative inducibility with inferior LV arrhythmic foci compared to anterior foci, i.e. 57.2±18.7% vs. 88.9±10.5%, respectively, at both 5 and 10 years (P=0.05). Recurrence was not related to intraoperative non-inducibility of VT or the presence of multiple morphological ventricular tachyarrhythmias.
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4. Discussion |
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TopAbstract1. Introduction2. Methods3. Results4. Discussion5. ConclusionReferences |
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4.1. Indications for VT surgery
Accepted indications for direct arrhythmia surgery include patients with drug refractory VT. However, in select lower risk patients, for example with non-ischaemic VT associated with an idiopathic LV aneurysm, surgical cure offers an attractive option. The alternative therapeutic modality for patients with VT refractory to medical therapy is either implantation of ICD or heart transplantation. The ICD is thought to be unsuitable for patients with frequent or incessant VT, which was the indication for urgent surgery in 27% of our patients as also reported by others [11].
4.2. Operative mortality and risk
Our overall 7.7% operative mortality was similar to that previously reported [4,7,8] and lower than the 25% reported by some [11]. The 8.3% operative mortality of our ischaemic VT was not related to poor preoperative functional class, as reported by others [11,15,16]. The predictive value of the LV ejection fraction measurements in patients with LV aneurysms is poor, and in practice we relied more on assessment of the residual non-aneurysmal LV contraction, albeit not formally scored. Other reported risk factors for operative mortality include poor LV wall motion score [11], emergency surgery [11,17], recent myocardial infarction [11], lack of a true LV aneurysm [15,16], an age of >65 years [7,18], bypass time [19], and incomplete revascularization [20]. Preoperative amiodarone therapy is also thought to increase operative risks [19]. The operative risk of concomitant mitral or tricuspid valve surgery that we observed has not been previously reported.
Rastegar and co-workers reported a 0% operative mortality in patients with true LV aneurysms (96% of which were anterior in this study), which are known favourable risk factors [9]. Similarly, the 2.6% mortality of Frapier and co-workers only included patients with VT following anterior myocardial infarctions [10]. Preoperative patient selection undoubtedly directly influences surgical results, and in our series we did not exclude patients who did not have true LV aneurysms or an inferior location per se, but placed most emphasis on the adequacy of non-aneurysmal ventricular contraction.
4.3. Recurrence of VT
Early postoperative EPS induced VT in only one of our patients (4% of ischaemic VT patients), in contrast to the 37% incidence reported by Lee and co-workers [7]. These observed differences in the recurrence of VT may be related to the surgical technique: our routine use of extended endocardial resection of all visible scars vs. the local or regional limited endocardial resection of Lee and co-workers [7]. More than one VT morphology was present in 31% of our patients and we believe would support the use of more extensive techniques. Krafchek and co-workers also showed a lower recurrence rate in patients with more extensive regional procedures than localized subendocardial resections [21]. Surgical ‘failure’ (postoperative induction or recurrence of VT) occurred in 17% of all our operative survivors and is similar to that reported by others [8,11], but lower than the 35–50% failure of direct VT surgery reported by some [22]. We identified a higher incidence of recurrence in patients in whom the arrhythmic focus was remote to the LV aneurysm, and VT recurrence tended also to be associated with the absence of a definite LV aneurysm or the presence of an inferior focus, as reported by others [7,11,14]. This again highlights the pathophysiological etiology of ventricular tachyarrhythmias, in originating from micro reentrant circuits in areas of ‘non-uniform’ myocardium containing both scar tissue and viable myocardium and not from ‘uniform’ scar tissue.
Surgery within 3 months of a myocardial infarction has also been identified as a risk for surgical ‘failure’ [23]. The recurrence in both patients undergoing only cryoablation probably reflected the lack of a true aneurysm and definitive endocardial scar tissue, and an inability of the cryosurgical technique used to completely ablate the arrhythmogenic intramural foci in these patients. At normothermia N2O cryolesions are unlikely to go deeper than 4–6 mm into the myocardium, and simultaneous endo- and epicardial or biventricular cryoablation for septal foci as well as new cryogens may offer a better option in such patients.
Frapier and co-workers reported a 5-year freedom from VT recurrence of 77% in post-anterior myocardial infarction patients undergoing encircling cryoablation without mapping and no endocardial resection [10]. This compares to our higher 5- and 10-year freedom from VT recurrence in an equivalent ‘selected’ group of patients with anterior foci of 88.9%, similar to that reported by Ferguson and co-workers [8]. We also believe that intraoperative EPS and mapping as well as extended endocardial resection, although more time-consuming, remain important surgical techniques [4,5]. Van Hemel and co-workers reported a high 50% failure of direct VT surgery and used map guided local and extended endocardial resection only [22]. Lee and co-workers reported surgical ‘failure’ of 36% and used either limited local or regional subendocardial resection to only the mapped focus as well as cryoablation [7], whereas Dor and co-workers used non-guided extended endocardial resection and obtained a 10% ‘failure’ rate [6]. Rastegar and co-workers had a similar 12% ‘failure’ with map guided local endocardial resection combined with cryoablation [9]. Despite an 18% surgical ‘failure’ in terms of curing ischaemic VT, the VT in our patients could be now easily controlled in contrast to their preoperative state, as reflected in our 0% incidence of sudden cardiac death on follow-up, which compares favourably to other reports of up to 18% [3]. Arrhythmia surgery techniques undoubtedly influence the incidence of post-arrhythmia surgery VT recurrence, and it would appear that more liberal or extensive surgical techniques in terms of mapping, endocardial resection and cryoablation offer improved success. Our results support the continued use of intraoperative map guided techniques, extended endocardial resection and extensive use of cryoablation.
4.4. Long-term survival
The 54.1% 5-year survival of our ischaemic VT patients was similar to the 54–59% reported by others [8,9,11,22] and of note is that no late deaths were arrhythmic or sudden. Factors influencing long-term survival of patients with malignant ventricular arrhythmias include congestive heart failure class, ejection fraction [2], extent of coronary artery disease [24], as well as VT recurrence following VT surgery [15]. Tendencies that we observed for long-term survival were the need for urgent or emergent VT surgery because of recurrent or incessant life-threatening VT (P=0.08), as well as preoperative NYHA class (P=0.06). Neither preoperative LV ejection fraction nor early postoperative LV function were risk factors in our series, possibly because of a lack of statistical power, although all late deaths were due to cardiac failure. The 5-year survival of our ischaemic VT patients (88% of whom were in NYHA class III or IV) is better than the reported survival of congestive heart failure class 3 and 4 VT patients treated with drug therapy (25% 5-year survival) or with an ICD (47% 5-year survival) [2]. As suggested by Gomes and co-workers this might be due to the positive effect of concurrent coronary revascularization [2]. However, the 6-year survival of coronary artery bypass surgery in patients with poor LV function (ejection fraction less than 20%) of 34% is less than that of our ischaemic VT patients [25]. Our 5- and 10-year survival of 73.3% in ischaemic VT patients not requiring urgent or emergent intervention because of immediate life-threatening VT possibly more accurately reflects the surgical results in patients that would be suitable for ICD implantation. Nevertheless, initial presentation in class IV heart failure with intractable ventricular arrhythmias does not preclude long-term survival with excellent function in suitable patients.
The importance of LV function in long-term survival is well known. Arrhythmia surgery when combined with LV remodelling of aneurysms can assist in discounting the negative influence of congestive heart failure class, as observed by Gomes and co-workers [2]. In our series LV reconstruction was based on the principles of Jatene [12], and improved LV ejection fraction by an average increase of 72%. Closure of the LV cavity was then by endoaneurysmorrhaphy with either a Dacron patch, or a bovine or autologous (immersed for 10 min in 0.625% glutaraldehyde) pericardial patch in the majority of patients, as previously described [9,13,16]. Ventricular remodelling of an aneurysmal LV may be the most important contributing factor determining long-term survival of direct VT surgery in these patients.
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5. Conclusion |
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TopAbstract1. Introduction2. Methods3. Results4. Discussion5. ConclusionReferences |
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Footnotes |
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References |
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TopAbstract1. Introduction2. Methods3. Results4. Discussion5. ConclusionReferences |
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