Hossein G Almassi, Sharon A Pecsi, Joseph F Collins, Laurie A Shroyer, Marco A Zenati, and Frederick L Grover. 2012. “
Predictors and impact of postoperative atrial fibrillation on patients' outcomes: a report from the Randomized On Versus Off Bypass trial.” J Thorac Cardiovasc Surg, 143, 1, Pp. 93-102.
AbstractOBJECTIVE: The study objective was to determine the predictors of postoperative atrial fibrillation (POAF) in patients randomized to conventional coronary artery bypass graft (on-pump coronary artery bypass [ONCAB]) versus beating heart coronary surgery (off-pump coronary artery bypass [OPCAB]).
METHODS: The subgroup of 2103 patients (of 2203 enrollees) in the Randomized On Versus Off Bypass trial with no POAF was studied (1056 patients in the ONCAB group and 1047 patients in the OPCAB group). Univariate and multivariate analyses were used to identify the predictors of POAF and the impact of POAF on outcomes.
RESULTS: Use of ONCAB versus OPCAB was not associated with increased rates of POAF. Older age (P < .0001), white race (P < .001), and hypertension (P < .002) were predictors of POAF on multivariate analysis. In general, POAF led to a higher rates of reintubation (ONCAB: 6.3% vs 0.8% no POAF, P < .001; OPCAB: 7.4% vs 1.8% no POAF, P < .0001) and prolonged ventilatory support (ONCAB: 7.1% vs 2.3% no POAF, P = .001; OPCAB: 9.2% vs 3.4% no POAF, P = .0003). The rate of any early adverse outcome was higher in patients with POAF (all patients: 10% POAF vs 4.7% no POAF, P < .0001; ONCAB: 9% POAF vs 4.3% no POAF, P = .008; OPCAB: 11% POAF vs 5.1% no POAF, P = .001). The 1-year all cause mortality was higher with POAF for both groups (ONCAB: 5.4% POAF vs 2% no POAF, P = .009; OPCAB: 5.1% POAF vs 2.6% no POAF, P = .07). POAF was independently associated with early composite end point (odds ratio [OR], 2.23; confidence interval [CI], 1.55-3.22; P < .0001), need for new mechanical support (OR, 3.25; CI, 1.39-7.61; P = .007), prolonged ventilatory support (OR, 2.93; CI, 1.89-4.55; P < .0001), renal failure (OR, 5.42; CI, 1.94-15.15; P = .001), and mortality at 12 months (OR, 1.94; CI, 1.14-3.28; P = .01).
CONCLUSIONS: In the Randomized On Versus Off Bypass trial, the strategy of revascularization did not affect the rate of POAF. Age, race, and hypertension were predictors of POAF. POAF was independently associated with a higher short-term morbidity and higher 1-year mortality rates.
NA Patronik, MA Zenati, and CN Riviere. 2012. “
A Study Ex Vivo of the Effect of Epicardial Fat on the HeartLander Robotic Crawler.” IFMBE Proc, 37, Part 1, Part 3, Pp. 227-230.
AbstractA tethered epicardial crawling robot known as HeartLander has been developed for minimally-invasive surgery on the beating heart. The crawler has been tested in vivo many times in a porcine model, a model which provides generally authentic conditions in many ways; however, the pigs tested generally have little epicardial fat, whereas the epicardial fat in human patients will be considerable. As a result, it is necessary to determine the effect of such fat on the performance of the crawler. In one experiment, using fresh ovine hearts ex vivo, clogging of the suction chambers of the crawler during sliding over tissue with active suction was investigated for a variety of thicknesses of epicardial fat. In a second experiment, the maximum traction force during each step was measured when sliding with active suction repeatedly over the same location for a variety of fat thicknesses. The clogging experiment showed accumulation of fat in the suction chamber, with the amount dependent on the state of the epicardial membrane, but the suction line did not clog. The traction experiment showed that traction was maintained in all cases except when the epicardial membrane was excised completely.
Nicholas A Patronik, Takeyoshi Ota, Marco A Zenati, and Cameron N Riviere. 2012. “
Synchronization of epicardial crawling robot with heartbeat and respiration for improved safety and efficiency of locomotion.” Int J Med Robot, 8, 1, Pp. 97-106.
AbstractBACKGROUND: HeartLander is a miniature mobile robot designed to navigate over the epicardium of the beating heart for minimally invasive therapy. This paper presents a technique to decrease slippage and improve locomotion efficiency by synchronizing the locomotion with the intrapericardial pressure variations of the respiration and heartbeat cycles.
METHODS: Respiratory and heartbeat phases were detected in real time using a chest-mounted accelerometer during locomotion in a porcine model in vivo. Trials were conducted over the lateral aspect of the heart surface to test synchronized locomotion against an unsynchronized control.
RESULTS: Offline evaluation showed that the respiration and heartbeat algorithms had accuracies of 100% and 88%, respectively. Synchronized trials exhibited significantly lower friction, higher efficiency, and greater total distance traveled than control trials.
CONCLUSION: Synchronization of the locomotion of HeartLander with respiration and heartbeat is feasible and results in safer and more efficient travel on the beating heart.
Nathan A Wood, David Schwartzman, Marco A Zenati, and Cameron N Riviere. 2012. “
Toward Onboard Estimation of Physiological Phase for an Epicardial Crawling Robot.” Proc IEEE RAS EMBS Int Conf Biomed Robot Biomechatron, 2012, Pp. 6290716.
AbstractHeartLander is a miniature mobile robot which adheres to and crawls over the surface of the beating heart to provide therapies in a minimally invasive manner. Although HeartLander inherently provides a stable operating platform, the motion of the surface of the heart remains an important factor in the operation of the robot. The quasi-periodic motion of the heart due to physiological cycles, respiration and the heartbeat, affects the ability of the robot to move, as well as localize accurately. In order to improve locomotion efficiency, as well as register different locations on the heart in physiological phase, two methods of identifying physiological phases are presented: sliding-window-based and model-based. In the sliding-window-based approach a vector of previous measurements is compared to previously learned motion templates to determine the current physiological phases, while the model-based approach learns a Fourier series model of the motion, and uses this model to estimate the current physiological phases using an Extended Kalman Filter (EKF). The two methods, while differing in approach, produce similarly accurate results on data recorded from animal experiments in vivo.