Chan, Edward Y. MD; Lumbao, Dennis M. MBA, BA; Iribarne, Alexander MD; Easterwood, Rachel BA; Yang, Jonathan Y. MD; Cheema, Faisal H. MD; Smith, Craig R. MD; Argenziano, Michael MD
Objective: For minimally invasive cardiac surgery (MICS) procedures requiring cardiopulmonary bypass (CPB), cannulation techniques vary and seem to be important determinants of technical difficulty and clinical outcomes. Over 10 years of MICS, we have modified our techniques substantially, and the present report outlines the evolution of our current cannulation platform.
Methods: From October 2000 to November 2010, 1087 minimally invasive cardiac procedures were performed at our institution; of these, 165 were done without CPB and were excluded. Methods of arterial and venous cannulation and aortic occlusion were retrospectively reviewed. Outcomes of interest included CPB and aortic cross-clamp time, as well as rates of in-hospital stroke, myocardial infarction, and short- and long-term mortality.
Results: The mean age of the study population was 57 ± 15 years, with 50% being men. The MICS procedures included mitral valve surgery, atrial septal defect repair, atrial fibrillation ablation, and cardiac tumor resections. Over the study period, peripheral arterial cannulation was replaced by central aortic cannulation, which was used in 33% of patients in 2000–2001 and 93% in 2008–2010. Venous cannulation strategies also evolved over time, from percutaneous neck and femoral (78% of cases from 2000–2005), to direct superior vena cava and percutaneous femoral (67% in 2006–2007), to percutaneous dual-stage femoral (51% in 2008–2010). Aortic occlusion was achieved by endoaortic balloon in 33% of cases in 2000–2001 but, by 2002, was replaced by transaxillary clamp occlusion and direct antegrade/retrograde cardioplegia. In the post-endoballoon era, CPB and cross-clamp times have remained consistent. Overall, there were nine strokes (<1.0%), no myocardial infarctions, and 18 deaths (2.0%) within 30 days of surgery, and the incidence of these outcomes has not changed over time.
Conclusions: Over 10 years, our cannulation strategy for MICS has evolved to favor central aortic over femoral arterial cannulation, percutaneous femoral dual-stage bicaval venous drainage over percutaneous neck access, and transaxillary clamping over endoaortic balloon occlusion of the aorta. In our experience, this approach has resulted in low complication rates and a reliable platform for a variety of MICS procedures.
Minimally invasive cardiac surgery (MICS) has experienced several major changes in philosophy and technique over the years. Cardiopulmonary bypass (CPB) has been used by surgeons during open heart cases since 1953, when the technique was first successfully employed.1 The advancement and improvement of laparoscopic general surgical technologies motivated the development of MICS, as Cosgrove2 first described in 1996. A key determinant of technical difficulty and clinical outcomes in MICS procedures requiring CPB seems to be cannulation techniques. Smaller incisions and tighter operative fields have necessitated smaller and more flexible cannulae. Similarly, improvements in transesophageal echocardiography technology have allowed for confirmation of cannula placement and verification of adequate deairing.3
Over 10 years of MICS, we have modified our cannulation techniques substantially. Our approach to CPB access has evolved from peripheral arterial cannulation to central aortic access and from percutaneously accessing the neck and femoral veins to using a dual-stage femoral vein cannula. In addition, aortic occlusion by endoaortic balloon was replaced by transaxillary clamp occlusion with direct antegrade and retrograde cardioplegia. We sought to analyze our institutional experience to elucidate the effect of cannulation technique on postoperative outcomes.
From October 2000 to November 2010, 1087 patients underwent MICS at our institution. Of this group, 165 did not have CPB during their operation and were excluded, leaving 922 operations. After institutional review board approval was obtained, data were acquired on patient demographics, operative variables, and postoperative complications from the New York State Cardiac Surgery database4 as well as our institutional medical records.
Operative records were analyzed to determine the type of arterial and venous cannulation, as well as the method of aortic occlusion. Arterial access was obtained with either central aortic cannulation or peripheral access via the femoral or axillary artery. Venous drainage included bicaval and direct right atrial access. Specific venous cannulation strategies were direct superior and inferior vena cavae (SVC and IVC) access, percutaneous right internal jugular (RIJ) and femoral access, and most recently, femoral vein with a dual-stage cannula. Aortic occlusion was achieved by endoaortic balloon and transaxillary aortic clamp application. In patients with a calcified aorta, CPB was used with ventricular fibrillation without aortic occlusion.
Primary outcome measures were short- and long-term mortality. Short-term mortality was defined as death within 30 days of surgery. Long-term mortality data were current as of March 22, 2011. Other outcomes of interest included stroke and major postoperative complications. Major complications include prolonged intubation (>72 hours), renal failure, reoperation for bleeding, sepsis, myocardial infarction, and unplanned cardiac reoperation. Survival data were obtained from the Social Security Death Index.5
Continuous variables were expressed as mean ± SD and were compared using Student t test. Categorical variables were compared using χ2 test. Long-term survival rates were calculated using the Kaplan-Meier method. Multivariate logistic regression (backward stepwise, removing P > 0.2) was used in the determination of factors associated with risk of postoperative complications. Multivariate Cox proportional hazards analysis (backward stepwise, removing P > 0.2) was used to determine the simultaneous effects of multiple factors on mortality. For all analysis, the level of statistical significance was set at P < 0.05. Stata 11.0 (StataCorp, College Station, TX USA) was used for statistical analysis of all data.
A total of 922 patients underwent elective MICS at our institution with CPB between October 2000 and November 2010. Demographic information is listed in Table 1 and separated by arterial cannulation type in Table 2. Within the study population, mean age was 57 ± 15 years, with 24.3% of patients older than 70 years and 5.5% of patients older than 80 years. Overall, 70.9% had at least one preoperative comorbidity or risk factor, with the most common being hypertension (41.6%), smoking (22.3%), and congestive heart failure (CHF, 15.7%). In our study population, 6.1% of the patients had undergone previous cardiac surgery. The cohort of patients who underwent peripheral cannulation was similar to the patients with central cannulation, except for a higher number of patients with CHF and previous cardiac surgery, likely because of the increased difficulty of achieving central cannulation in those patient populations.
The most common MICS operations were mitral valve procedures (612 cases, 66.4%), including 503 mitral valve repairs and 109 mitral valve replacements (Table 3). The next most common surgeries were atrial septal defect repair (13.6%), aortic valve replacement (9.1%), and resection of cardiac tumor (5.2%). Mean CPB time was 122 ± 53 minutes, and mean aortic cross-clamp (XC) time was 75 ± 36 minutes.
Overall, 793 (86%) of our patients had central aortic cannulation, whereas 125 (14%) underwent femoral artery access and 3 (0.4%) had axillary artery cannulation (Table 4). Venous drainage was performed in a bicaval manner in 758 (82%) patients, whereas direct right atrial drainage was performed in 119 (13%) patients. During the study period, peripheral arterial cannulation was progressively replaced by central aortic cannulation, which was used in 33% of patients in 2000–2001, 83% of patients from 2002–2005, and 93% of patients from 2008–2010 (Fig. 1). Venous cannulation strategies also evolved over time. Percutaneous neck and femoral access was predominantly used in 2000–2005 (78% of cases), progressing to direct SVC and femoral vein (67% from 2006–2007), and then to our current practice of percutaneous dual-stage femoral vein cannulation (51% of patients from 2008–2010). Aortic occlusion was achieved by endoaortic balloon in 33% of cases from 2000–2001 but, by 2002, was replaced by transaxillary clamp occlusion and direct antegrade and retrograde cardioplegia. In 66 cases, ventricular fibrillation was used instead of aortic occlusion, and these patients were excluded from analysis of aortic XC times and subsequent multivariate analyses. In the post-endoballoon era, CPB and XC times have remained consistent.
The median length of hospital stay was 5 days (interquartile range, 4–8). In-hospital complication rate was 9.1% (78 patients). Eight patients were converted from a minimally invasive to standard median sternotomy. Three patients unexpectedly required CPB during an operation intended to be off-bypass and were included in our analysis. The most common complications were prolonged intubation (40, 4.3%), bleeding requiring reoperation (22, 2.4%), and renal failure (12, 1.3%) (Fig. 2). Of the patients requiring reoperation for bleeding, none of the cases involved peripheral vascular complications. The overall rate of stroke was less than 1%, with three patients having strokes within 24 hours of surgery and six patients with strokes after 24 hours. Of these nine strokes, seven were ischemic in etiology and two were hemorrhagic. There were no myocardial infarctions or aortic dissections.
Using multivariate logistic regression, risk factors for any in-hospital complication included increased age, preoperative hepatic failure, and peripheral artery cannulation (Table 5). Preoperative immune deficiency approached statistical significance as a risk factor, whereas preoperative diagnosis of hypertension was found to be protective. When postoperative stroke was analyzed as the outcome of interest, aortic atherosclerosis increased the odds of an event by more than 10 times (Table 6). Preoperative stroke was also a significant risk factor for postoperative stroke.
Operative mortality was 2.0% (18 deaths within 30 days or in the same hospitalization), with previous cardiac surgery and increased age as significant risk factors (Table 7). Long-term survival was 82% at 10 years, with a total of 84 deaths. Cox proportional hazards analysis demonstrates that previous cardiac surgery, increased age, prior stroke, and preoperative congestive heart failure are significant risk factors for mortality (Table 8).
As MICS has evolved, so too have the strategies and approaches to CPB access. Early descriptions of MICS involve a parasternotomy incision with direct aortic, direct SVC, and percutaneous IVC access6 or ministernotomy with femoral artery, direct SVC, and percutaneous IVC cannulation.7 Shortly thereafter, the port-access system was developed and was widely adopted, which involved obtaining arterial access via the femoral artery and deploying a balloon to achieve endovascular aortic occlusion.8 Subsequent problems with peripheral vascular complications, aortic dissections, and strokes led to a decline in its use.
Over our 10-year experience with MICS, we have also seen a progression in our techniques. Early descriptions in the literature of MICS techniques predominantly involved peripheral arterial cannulation through the femoral artery. As we began our minimally invasive practice, our earliest operations involved similar methods, with femoral artery access and endoaortic balloon occlusion. With increased institutional experience and with the growing body of evidence that peripheral cannulation was associated with higher incidences of stroke and vascular complications,9 we developed our central cannulation technique that allowed preferential cannulation of the aorta. To minimize the risk of aortic dissection, we also replaced the endovascular balloon with a percutaneous transaxillary aortic XC that allowed for direct aortic occlusion.10,11
Similarly, our original cannulation techniques involved percutaneous bicaval venous drainage, with SVC access through the RIJ vein and IVC access from the right femoral vein. Drawbacks to this technique included location of the RIJ cannula outside our sterile operative field by anesthesia. In addition, we found the cannula to be cumbersome, and it created a large defect in the vein. We began using direct SVC and percutaneous femoral vein access. With the development of the dual-stage femoral vein cannula, we have changed our practice to achieve bicaval venous drainage through a single percutaneous venous access site. However, in cases where right atriotomy is necessary, we continue to use direct SVC and percutaneous IVC drainage. Adequacy of venous drainage was checked with central venous pressure monitoring and transesophageal echocardiography.
In assessing patients for appropriate cannulation techniques, numerous factors deserve consideration. When performing femoral artery cannulation, we ruled out patients with aortoiliac disease and small femoral arteries. Extensive aortic atherosclerosis was a contraindication for central aortic cannulation. Central cannulation was more challenging in patients with CHF and reoperative sternotomies, and as such, they were more commonly approached with peripheral arterial cannulation. Patients with IVC filters were not candidates for percutaneous venous cannulation via the femoral vein.
Minimally invasive cardiac surgery has been shown in numerous studies to have comparable mortality rates when compared with standard median sternotomy.12–16 Less invasive techniques have also been shown to result in decreased length of hospital stay, reduced postoperative pain, improved patient satisfaction, faster return to daily physical activities, and higher quality of life.7,13,15,17–21 However, serious concerns have been raised regarding increased morbidity associated with MICS. In particular, a greater number of strokes were seen in MICS patients in an analysis of the Society of Thoracic Surgeons Database.9 A meta-analysis of six papers did not find a similar increase in the number of neurological events.11 A propensity analysis comparing minimally invasive and median sternotomy mitral valve surgeries at our institution also did not find any increase in the relative number of strokes,15 a difference we attribute, in part, to our methods of central aortic cannulation, meticulous deairing, and direct aortic occlusion. The stroke rate of less than 1% in this study population reinforces that finding.
Limitations to our study include the retrospective nature of the analysis and the lack of patient-matched controls for different cannulation techniques across time periods. In addition, our information on complications was limited to those that occurred during the initial hospitalization. We did not have information on long-term neurological or functional status. We also attempted to examine differences in outcomes over time as our techniques changed, but the small number of events made adequate analysis impossible. In addition, given the low complication rate, we did not have the power to adequately examine risk factors associated with individual complications.
In our series, the mean CPB and aortic XC times of 122 and 75 minutes, respectively, demonstrate that despite a learning curve associated with new techniques, our cannulation strategies are feasible with reasonable operative times. Our stroke rate and the 9.1% in-hospital complication rate are acceptably low and comparable with those in large published reports.9 Multivariate logistic regression showed an increased risk of postoperative complication with peripheral arterial cannulation when compared with central aortic cannulation. In addition, increased age and preoperative hepatic failure were found to increase risk of complications. Not surprisingly, postoperative stroke was more common in patients with aortic atherosclerosis and a preoperative history of stroke. Operative mortality was 2.0%, with increased age and previous cardiac surgery as predictive risk factors. Long-term outcomes demonstrated 82% survival at 10 years, with previous cardiac surgery, increased age, and CHF as risk factors for death, according to Cox proportional hazard analysis.
Over 10 years, our cannulation strategy for MICS has evolved to favor central aortic over femoral artery cannulation, percutaneous femoral dual-stage bicaval venous drainage over percutaneous neck access, and direct transaxillary clamping over endoaortic balloon occlusion of the aorta. In our experience, this approach has resulted in low complication rates and a reliable platform for a variety of MICS procedures.
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This retrospective, observational study examined the evolution of cannulation techniques for minimally invasive cardiac surgery at a busy academic center. The authors examined more than 1000 cases during a 10-year period. Their cannulation techniques evolved over this time to favor central over femoral arterial cannulation and percutaneous dual-stage femoral venous drainage over percutaneous neck access. They also moved from endoaortic balloon clamping of the aorta toward direct clamping via a transaxillary approach. They suggested that this evolution has played a role in their low complication rate and excellent outcomes.
This is an important contribution to the literature from one of the pioneering groups in minimally invasive cardiac surgery. It is noteworthy for the number of patients and the length of their experience. However, the study suffers from its nonrandomized nature and its inadequate power to adequately discriminate and compare the complication rates of the different cannulation strategies.
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