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Biomedical subjects

Robert D Dowling

Publications and source records attributed to Robert D Dowling.

16 recordsLinked to original sources

Simple mechanical aortic valve closure in ventricular assist device recipients.

Patients with mechanical aortic valves that develop refractory heart failure may require left ventricular assist devices. These patients have an increased risk of postoperative thromboembolic events due to intermittent valve opening. Previously described techniques to address this problem can result in a significantly increased ischemic time. We describe a simple but novel technique to close the mechanical aortic prosthesis in an expeditious manner.

Aortic Valve↗

Improved technique to diagnose a patent foramen ovale during left ventricular assist device insertion.

Diagnosis of a patent foramen ovale prior to left ventricular assist device placement can be quite difficult, and if missed may result in a significant hypoxemia due to a right to left shunt. We describe a simple and precise way to increase the diagnostic accuracy of patent foramen ovale detection prior to initiating cardiopulmonary bypass for left ventricular assist device placement.

Adult↗

Traumatic intramyocardial left ventricular dissection: a case report.

In this report, we present an unusual case of a patient who sustained and survived an intramyocardial dissecting hematoma with subacute ventricular rupture complicating a motor vehicle accident. In conclusion, we report on the diagnosis, management, and prior literature of this highly unusual and often lethal condition.

Accidents, Traffic↗

Transcatheter closure of patent foramen ovale after left ventricular assist device implantation: intraoperative decision making.

The presence of a patent foramen ovale in patients with heart failure can be missed during echocardiography despite the use of provocative maneuvers. Implantation of a left ventricular assist device in these patients can result in right-to-left shunting and hypoxemia. We report the use of a percutaneous atrial septal defect closure device as an alternative to surgical closure.

Cardiopulmonary Bypass↗

Transmyocardial revascularization: 5-year follow-up of a prospective, randomized multicenter trial.

BACKGROUND: In prospective randomized trials at 1 year, transmyocardial revascularization (TMR) provided superior relief of angina, decreased rehospitalizations, and improved exercise times. We evaluated 5-year mortality and angina class in "no-option" patients with diffuse coronary artery disease randomized to TMR or continued medical management. METHODS: Two hundred twelve patients with refractory class IV angina who were not candidates for conventional therapy were randomized to receive holmium:yttrium-aluminum-garnet TMR (n = 100) or continued medical management (n = 112) at nine centers. Follow-up included all-cause mortality along with angina class assessment by blinded evaluators. Mean follow-up was 5.7 +/- 0.8 years. RESULTS: Mean angina scores for TMR patients were 4.0 +/- 0.0 at baseline, 1.5 +/- 1.4 at 1 year, and 1.2 +/- 1.1 at a mean of 5 years (p < 0.001). After an average of 5 years, a significantly greater proportion of TMR than medical management patients experienced two or more class improvement in angina (88% versus 44%; p < 0.001). Kaplan-Meier intention-to-treat survival at 5 years was 65% versus 52% (TMR versus medical management; p = 0.05). Cumulative hazard curves demonstrated a significantly reduced risk of late death for TMR patients; average annual mortality beyond 1 year was 8% versus 13% (TMR versus medical management; p = 0.03). CONCLUSIONS: Five-year follow-up of prospectively randomized, no-option class IV angina patients demonstrated significantly increased Kaplan-Meier survival in patients randomized to TMR. The significant angina relief observed 12 months after sole therapy TMR was sustained long term and continued to be superior to that observed for patients maintained on continued medical management alone.

Angina Pectoris↗

Adjunctive transmyocardial revascularization: five-year follow-up of a prospective, randomized trial.

BACKGROUND: In a prospective, randomized trial involving 263 patients who would be incompletely revascularized by coronary artery bypass grafting (CABG) alone, CABG plus transmyocardial revascularization (CABG/TMR) provided an early mortality benefit with similar angina relief compared with CABG alone at 1 year. We evaluated the long-term outcome of patients randomized to CABG/TMR or CABG alone. METHODS: Thirteen centers that enrolled 83% (218/263) of the patients in the original trial participated in this longitudinal study. Between 1996 and 1998, these centers randomized 218 patients who would be incompletely revascularized by CABG alone because of diffusely diseased target vessels to either holmium:yttrium-aluminum-garnet (holmium:YAG) CABG/TMR (n = 110) or CABG alone (n = 108). Baseline demographics and operative characteristics were similar between groups. Follow-up (mean 5.0 +/- 1.7 years) included survival and blinded angina class assessment. RESULTS: At this 5-year follow-up both groups experienced significant angina improvement from baseline, however, the CABG/TMR group had a lower mean angina score (0.4 +/- 0.7 vs 0.7 +/- 1.1, p = 0.05), a significantly lower proportion of patients with severe angina (class III/IV: 0% [0/68] vs 10% [6/60], p = 0.009), and a trend towards greater number of angina-free patients (78% [53/68] vs 63% [38/60], p = 0.08), compared with CABG alone patients. Kaplan-Meier survival at 6 years was similar between CABG/TMR and CABG alone patients (76% vs 80%, p = 0.90). CONCLUSIONS: Five-year follow-up of prospectively randomized patients who would be incompletely revascularized because of diffuse coronary artery disease indicates that the addition of TMR to conventional CABG provides superior angina relief compared to CABG alone.

Aged↗

Initial experience with the AbioCor implantable replacement heart system.

OBJECTIVE: We sought to evaluate the safety and efficacy of the first available totally implantable replacement heart (AbioCor Implantable Replacement Heart System) in the treatment of severe, irreversible biventricular heart failure in human patients. METHODS: Seven male adult patients with severe, irreversible biventricular failure (>70% thirty-day predicted mortality) who were not candidates for transplantation met all institutional review board study criteria and had placement of the AbioCor Implantable Replacement Heart. All were in cardiogenic shock despite maximal medical therapy, including inotropes and intra-aortic balloon pumps. Mean age was 66.7 +/- 10.4 years (range, 51-79 years). Four of 7 patients had prior operations. Six had ischemic and one had idiopathic cardiomyopathy. All had 3-dimensional computer-simulated implantation of the thoracic unit that predicted adequate fit. At the time of the operation, the internal transcutaneous energy transfer coil, battery, and controller were placed. Biventriculectomy was then performed, and the thoracic unit was placed in an orthotopic position and attached to the atrial cuffs and outflow conduits with quick-connects. The flow was adjusted to 4 to 8 L/min. Central venous and left atrial pressures were maintained at 5 to 15 mm Hg. The device is powered through transcutaneous energy transfer. An atrial flow-balancing chamber is used to adjust left/right balance. The balance chamber and transcutaneous energy transfer eliminate the need for percutaneous lines. RESULTS: There was one intraoperative death caused by coagulopathic bleeding and one early death caused by an aprotinin reaction. There have been multiple morbidities primarily related to preexisting illness severity: 5 patients had prolonged intubation, 2 had hepatic failure (resolved in 1), 4 had renal failure (resolved in 3), and 1 each had recurrent gastrointestinal bleeding, acute cholecystitis requiring laparotomy, respiratory failure that resolved after 3 days of extracorporeal membrane oxygenation, and malignant hyperthermia (resolved). There were 3 late deaths: one caused by multiple systems organ failure (postoperative day 56), one caused by a cerebrovascular accident (postoperative day 142), and one caused by retroperitoneal bleeding and resultant multiple systems organ failure (postoperative day 151). This latter patient was not able to tolerate anticoagulation (no anticoagulation or antiplatelet therapy alone for 80% of the first 60 days) and had a transient ischemic attack on postoperative day 61 and a cerebrovascular accident on postoperative day 130. At autopsy, blood pumps were clean. The 2 patients who had large cerebrovascular accidents had thrombus on the atrial cage struts. These struts have been removed for future implants. There has been no significant hemolysis or device-related infections. The balance chamber has allowed for left/right balance in all patients (left atrial pressure within 5 mm Hg of right atrial pressure). Three patients have taken multiple (>50) trips out of the hospital, and 2 have been discharged from the hospital. Total days on support with the AbioCor are 759. CONCLUSION: The initial clinical experience suggests that the AbioCor might be effective therapy in patients with advanced biventricular failure. There have been no significant device malfunctions. Two of these patients have been discharged from the hospital.

Aged↗

The total artificial heart: where we stand.

The AbioCor total artificial heart (TAH) is undergoing clinical feasibility testing as destination therapy in patients with end-stage congestive heart failure. So far, the device has been implanted in 11 of a projected 15 patients. The TAH has performed reliably, providing adequate circulatory support while extending survival and improving quality of life in most recipients. Thromboembolism remains a problem but is being addressed by optimizing device and patient management and refining the anticoagulation protocol. Because the device is totally implantable and requires no penetration of the skin, infection has been minimized. All recipients so far have been men. The device is large and this limits its use in smaller patients (i.e. women, small men and children). A smaller version is being developed. Although it has yet to receive Food and Drug Administration approval, the early clinical results suggest that the AbioCor TAH may become an accepted alternative to heart transplantation for selected patients with end-stage congestive heart failure. Further investigation with regard to its primary clinical applicability, i.e. as a rescue device for sudden catastrophic heart failure, is warranted.

Aged↗

The AbioCor implantable replacement heart.

The AbioCor implantable replacement heart (IRH) is the first available totally implantable artificial heart. We recently initiated a multicenter trial of this device in patients with severe, irreversible biventricular failure. Patients who were not candidates for other therapies, including transplantation, were evaluated. All candidates were adults with inotrope-dependent biventricular failure, whose 30-day predicted mortality was higher than 70%. A three-dimensional computerized fit study predicted fit of the AbioCor thoracic unit in all recipients. At operation, the internal battery controller and transcutaneous energy transfer unit were placed. The AbioCor thoracic unit was placed in an orthotopic position after incision of the ventricals. There were 2 intraoperative deaths (due to intraoperative bleeding or aprotinin reaction). Four late deaths were recorded, 1 from multisystem organ failure and 3 cerebrovascular accidents. Autopsy revealed thrombus on the atrial struts of the 3 patients with cerebrovascular accident. Blood pumps and valves were clean on all patients. Significant morbidity was observed, primarily related to preexisting severity of illness. However, 3 patients recovered to the point of being able to take multiple trips outside of the hospital. Two patients were discharged from the hospital, with 1 patient being discharged home for more than 7 months. No significant device malfunctions or multi-system organ failure device-related infections were noted. The AbioCor IRH may be effective therapy for patients with end-stage heart failure. Many milestones have been achieved in the initial trial in humans, including the successful discharge of a patient to home and no significant device malfunctions. The occurrence of stroke is likely related to the presence of thrombus on the atrial struts and may be decreased as these atrial struts have been removed for future clinical implants.

Aged↗

Partial left ventriculectomy--The Third International Registry Report 2002.

BACKGROUND: An international registry of partial left ventriculectomy (PLV) has been expanded, updated, and refined to include 440 cases voluntarily reported from 51 hospitals in 11 countries. RESULTS: Gender, age, ventricular dimension, etiology, ethnology, myocardial mass, operative variation or presence or absence of mitral regurgitation as well as transplant indication had no effects on event-free survival, which was defined as either absence of death or ventricular failure requiring ventricular assist device or listing for transplantation. Preoperative patient condition such as NYHA functional class IV, depressed contractility, and decompensation requiring an emergency procedure were associated with reduced event-free survival. Other risk factors included early date of surgery, lack of experience, and extended myocardial resection. Performance of PLV reached a peak by 1998 and was largely abandoned by 2000 except in Asia, where experienced institutes continue to perform PLV in patients in better condition with preserved myocardial contractility. CONCLUSION: Avoidance of delineated risk factors appears to improve recent survival and may help stratify high- or low-risk patients for PLV. An integrated approach with mechanical and biological circulatory assist may improve prognosis for patients with dilated failing hearts. While frequency of PLV has decreased, the concept of ventricular volume reduction has been extended to other volume reduction procedures and less invasive procedures now under clinical trial.

Adolescent↗

Treadmill exercise in calves implanted with the AbioCor replacement heart.

The aim of this study was to evaluate the function of the AbioCor artificial heart implanted in calves that underwent treadmill exercise testing and to investigate the cardiovascular and metabolic responses during exercise. Six calves were implanted with the AbioCor. One week after surgery, exercise training was undertaken and animals were put on a treadmill at a speed of 0.5-1.0 mph, with the AbioCor operating at the maximum heart rate of 150 beats per minute. During exercise, the left and right atrial pressures were significantly increased (p < 0.05). Oxygen consumption was significantly elevated (p < 0.05). Lactate levels did not significantly increase (p > 0.05). The index of metabolic adequacy remained higher than 2.0, indicating that there was no substantial transition to anaerobic metabolism during exercise. There was an increased extraction of oxygen during exercise to meet the increased energy demands. Our study demonstrated that animals implanted with the AbioCor heart were able to maintain aerobic metabolism during low levels of exercise testing.

Animals↗

Development and early testing of a simple subcutaneous counterpulsation device.

The intra-aortic balloon pump has been widely and successfully used as a treatment for cardiac dysfunction, but it only has short-term applications. To overcome this limitation, a superficial counterpulsation device (CPD) is being developed to provide extended counterpulsation support to promote myocardial recovery. The CPD is a valveless, monoport, pneumatically driven, 40-ml sac that is intended to be implanted in a pacemaker-type pocket in the subclavian fossa. The sac is designed to fill in systole and empty during diastole through an outflow graft anastomosed to the subclavian artery. A feasibility study was conducted to investigate acute hemodynamic responses to the CPD in eight calves with diminished cardiac function. The CPD augmented aortic diastolic pressure, reduced left ventricular peak systolic and aortic ejection pressures by up to 18%, and increased diastolic coronary flow by up to 21% and stroke volume by up to 12%. A cadaver fit study demonstrated that the human subclavian artery is a reasonable anastomosis site to consider and that the 40-ml CPD needs to be reduced in size to provide a better anatomical fit. The clinical attractiveness of this approach is that it may provide extended support through a subcutaneous surgical procedure.

Animals↗

Left ventricular volume reduction surgery: The 4th International Registry Report 2004.

BACKGROUND AND METHODS: An international registry of left ventricular volume reduction (LVVR) procedures, including partial left ventriculectomy, has been expanded, updated, and refined to include 568 cases voluntarily reported from 52 hospitals in 12 countries. RESULTS: Gender, age, ventricular dimension, ethnology, myocardial mass, presence or absence of mitral regurgitation, as well as transplant indication, had little effect on event-free survival, which was defined as either absence of death or ventricular failure requiring mechanical assist or transplantation. Poor preoperative patient condition such as New York Heart Association classification IV, depressed contractility and decompensation requiring an emergency procedure were associated with reduced event-free survival. Other risk factors included an early surgery date, lack of experience, dilated cardiomyopathy as the underlying pathology and extended myocardial resection. Performance of LVVR reached a peak by 1998, but was largely abandoned by 2001, except in Asia, where experienced institutes continue to perform it in patients in better condition with preserved myocardial contractility. CONCLUSION: Avoidance of risk factors appears to have contributed to the recent survival improvement and may help stratify patients for LVVR. While performance has been decreasing, the concept has been extended to other LVVR and less invasive procedures, which are now under clinical trials.

Adolescent↗