Transapical transcatheter aortic valve replacement in patients with or without prior coronary artery bypass graft operation

Redo cardiac surgery is associated with an increased risk of morbidity and mortality in comparison with an initial cardiac operation [1‐3]. In patients with prior coronary artery bypass grafting (CABG) and patent grafts undergoing reoperation for surgical aortic valve replacement (SAVR), in addition to technical issues related to cicatrix formation and dissection, myocardial protection and prevention of graft injuries are concerns that require careful surgical management [3, 4].

Transcatheter aortic valve replacement (TAVR) has shown good early and mid-term results in patients with severe aortic stenosis and various comorbidities or inoperable patients [5‐7]. High-risk or inoperable patients with severe aortic stenosis who had previously undergone cardiac surgery represent a particularly challenging group that could benefit from a minimally invasive trans-catheter approach. Trans-apical (TA) TAVR has become an alternative access site for the treatment of high-risk patients with severe symptomatic aortic stenosis. Because of the minimally invasive nature of this approach, TA-TAVR has become particularly attractive in high-risk patients with prior cardiac surgery [8, 9]. However up to now the impact of prior CABG on the clinical outcome after TA-TAVR has yet to be defined. The purpose of the present study was to compare outcomes of patients with prior CABG undergoing TA-TAVR with those undergoing TA-TAVR as an initial procedure.

This study demonstrates that prior CABG in patients undergoing TA-TAVR does not impair clinical outcome. Patients with CABG presented herein had a clearly elevated risk profile as expressed by a higher STS risk score, an increased prevalence of dyslipidemia, diabetes, previous myocardial infarction and significant left main stenosis, and a lower left ventricular ejection fraction. Despite the high risk profile, procedural aspects, post-procedural complication rates, and one-year clinical outcome, were comparable between the two groups; one-year survival was 81.8 and 77.8% for patients with and without prior CABG respectively (p = 0.509). Interestingly, patients with prior CABG exhibited a smaller incidence of new onset atrial fibrillation (p = 0.016). However, on multivariate analysis new onset atrial fibrillation did not significantly increase the hazard for one-year mortality. Conduction abnormalities and permanent pacemaker placement rate were comparable between the two groups. Echocardiography measurements of the aortic valve were similar both at 30 days and at one year and changes on left ventricular ejection fraction at follow up were not statistically different in both groups of patients. The only predictor for mortality on multivariate analysis was history of stroke.

TAVR has been documented to be safe and effective in inoperable patients with severe aortic stenosis and has also emerged as an alternative to open SAVR in high-risk patients with severe aortic stenosis [5, 6]. Patients undergoing cardiac re-operation consist a high-risk subgroup [12]. Despite previous reports showing that SAVR can be performed safely and with excellent outcomes in patients with prior CABG [13, 14], the risk of mortality and morbidity in this subgroup is higher. Repeat sternotomy pose the risk of coronary graft injury during re-entry to the mediastinum and difficulty in myocardial protection as well as potential traumatic injury and hemorrhage [3, 12]. Moreover, multiple co-morbidities render this population as a surgically challenging group. Thus, TAVR has been suggested as a viable option in these patients. The proportion of TAVR patients with prior CABG has been reported to range from 25.5 to 42% [15]. TAVR patients with a history of prior cardiac surgery have documented to be younger and have more co-morbidities, such as diabetes, porcelain aorta, peripheral vascular disease and poor left ventricular ejection fraction compared with patients without previous cardiac operation [2, 15].

Several studies have shown the feasibility of TAVR in patients with prior CABG regardless of the access site. On multivariate analysis of PARTNER I trial, where high-risk patients with severe aortic stenosis were randomized to SAVR or TAVR, prior CABG was shown to have no impact on prognosis after TAVR [16]. In a subgroup analysis of the same trial no differences between patients with previous cardiac operation following TAVR vs SAVR in terms of operative outcomes were found; however, a trend towards greater all-cause mortality was seen in the TAVR group at 2 years [17]. Similarly, in a recent report from the European SOURCE XT registry, which included 2.688 patients who underwent TAVR with the SAPIEN XT valve, prior CABG was not associated with one year mortality [18]. These findings are in accordance with data from FRANCE 2 Registry in which 30-day and one-year mortality from all causes did not differ according to history of CABG [19]. Moreover, there were no significant differences in VARC complications (myocardial infarction, stroke or vascular and bleeding complications). On multivariate analysis, CABG was not associated with greater one year post-TAVR mortality. In their study of 201 patients, 140 (70%) of whom underwent TAVR through trans-arterial approach and 61 patients through TA approach, Ducrocq et al. reported similar mortality rates in TAVR patients irrespective of prior CABG history and concluded that TAVR is an attractive option in high risk population with symptomatic severe aortic stenosis and previous heart surgery [8].

Currently, only a few studies have reported on prognosis after TA-TAVR in relation to prior CABG and the exact impact of previous cardiac operation on mortality after TA-TAVR is not well established. In a retrospective study of 566 patients, 110 (19.4%) with a history of prior CABG, who underwent TA-TAVR from the Italian Registry all-cause and cardiovascular mortality at 30 days and survival at one and two years were similar between patients with and without prior CABG [2]. Additionally, there were no significant differences between the two groups in terms of post-procedure complications. In line with the above study, no differences in the short-term and long-term mortality were documented between propensity-matched subgroups of 45 TAVR patients with and 45 TAVR patients without prior CABG in a study by Papadopoulos et al. [20]. Echocardiography at 4 years showed no differences in left ventricular ejection fraction, effective orifice valve area and mean trans-valvular gradient between the two groups in this study. The findings of the above studies were also comparable with reports by Drews et al. [21], and Walther et al. [22] and indicate that prior CABG does not have a significant impact morbidity and mortality in patients undergoing TA-TAVR.

Our results are in accordance with the existing literature. Mortality at six months and one year follow up were similar between the two groups, while echocardiography data at 30 days and one year with respect to aortic valve orifice, and trans-valvular gradient were not different. Moderate/severe mitral valve regurgitation frequency at 30 days and one-year after valve implantation was similar between the two groups and improved from the pre procedure one. Toggweiler et al. in their study on patients with moderate and severe mitral valve regurgitation had previously reported an improvement in mitral regurgitation in 55% of patients with moderate or severe MR after TAVR at one-year follow up [23]. Additionally, a lower incidence of new onset atrial fibrillation was observed post-procedure in patients with prior CABG (11.1 vs. 30.9%, p = 0.016). Higher prevalence of permanent pacemaker and implantable cardioverter defibrillator observed preoperatively in the CABG population could account for this finding. Yet, when adjusted for presence of permanent pacemaker and implantable cardioverter defibrillator, incidence of atrial fibrillation remained significantly higher in the non CABG population (p = 0.024). Furthermore, on multivariate analysis new onset atrial fibrillation was not predictor for all-cause mortality at one year. Cardiac surgery has been shown to increase susceptibility to atrial fibrillation in previous studies [24, 25]. In our study the prevalence of pre procedure atrial fibrillation was not statistically different in patients with prior CABG (44.4 vs. 33.3%, p = 0.251). The deleterious impact of atrial fibrillation on TAVR patients was recently underscored in a sub-analysis from PARTNER trial [26]. Patients who converted from sinus rhythm to atrial fibrillation by discharge had the highest rates of all-cause mortality at 30 days (adjusted HR = 3.41; p = 0.0002) and over 2-fold difference at 1 year (adjusted HR = 2.14; p < 0.0001). The presence of atrial fibrillation on baseline or discharge ECG was a predictor of one-year mortality. Similarly, in the FRANCE 2 Registry pre-existing and new-onset atrial fibrillation are both associated with higher mortality and morbidity after TAVR [27]. In another study new onset atrial fibrillation was detected in 21% of patients; 50% of all the episodes occurred in the initial 24 h after the procedure [28]. TA approach was observed to an important predictor of new onset atrial fibrillation and is associated with a prolongation of intensive care unit and hospital stay. In a recent meta-analysis of twenty-six studies, 14,078 patients undergoing TAVR, of whom 33.4% had pre-existing atrial fibrillation and 17.5% had new onset atrial fibrillation, were assessed for early and long-term all-cause mortality, cardiovascular mortality and cerebrovascular events. New onset atrial fibrillation patients showed similar short- and long-term all-cause mortality when compared to patients in sinus rhythm, whereas a non-significant increase in the incidence of cerebrovascular events was observed at long-term follow-up [29]. On the same line in another study new onset atrial fibrillation was not associated with higher stroke or mortality rates at 30 days or one year of follow-up [30]. In multivariate analysis, atrial fibrillation pre-procedure but not new onset atrial fibrillation was a significant predictor of mortality throughout the follow-up period (HR 2.2, p = 0.003 at 30 days, and HR 1.5, p = 0.39, respectively).

From the technical point of view, procedure duration in hours, life threatening bleeding and units of blood transfused were not different between patients with and without prior CABG supporting the concept that chest reentry during TA-TAVR does not represent a substantial surgical challenge. Increased incidence of major bleeding was observed in both groups, a finding related to a combination of low baseline hemoglobin with modest peri-procedural blood loss on a high risk population. An identifiable source of bleeding was present in only a few cases and no statistical significant difference in the incidence was observed between the two groups. Our results show that adhesions and scar tissue in the apical area were not limiting factors for chest re-entry through apical access. In fact, the presence of adhesions may actually prevent myocardial tissue trauma and hemorrhage after valve implantation and apical closure, as shown by the lack of peri-operative myocardial infarction in our study patients. The potential role of patent grafts on minimizing the consequences of coronary ostia obstruction by calcium displacement or debris embolization of the coronary arteries following prosthetic valve deployment is a possible explanation for the above findings as well.

Permanent neurologic defects remain a concern in high-risk patients undergoing cardiac surgery. Stroke rate in our study, was 1.2% for patients without and 0% for patients with prior CABG undergoing TA-TAVR and were in accordance with previously published data after TA-TAVR in patients with and without prior CABG [8, 9, 31, 32]. Furthermore, history of stroke was the only predictor of one year mortality on multivariate analysis. This improvement in the prevalence of stroke certainly represents a powerful advantage of TA-TAVR in high risk patients.

TA TAVR in patients with prior CABG appears to be safe and can be carried out with similar results in terms of mortality compared with patients undergoing TAVR as their first cardiac operation. TA-TAVR represents an alternative treatment option to redo SAVR in this high risk population. The decision regarding the final treatment approach should be individualized on each single patient after taking into consideration age, the associated co-morbidities and the need for revascularization.