Temporary mechanical support.
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Assisted Circulation↗
Biomedical subjects
N Moazami
Publications and source records attributed to N Moazami.
Transluminal aortic valve placement. A feasibility study with a newly designed collapsible aortic valve.
Percutaneous stents are used in vascular applications in conjunction with angioplasty and in combination with graft material for repair of abdominal aneurysms. The authors have designed a collapsible bioprosthetic aortic valve for placement by a transluminal catheter technique. This trileaflet stent valve is composed of stainless steel and bovine pericardium. Stent valves, 23 and 29 mm, were tested in a pulse duplicator system with rigid rings from 21 to 31 mm in 2 mm increments. At a mean flow of 3.1 L/min (+/-0.7), normal systemic aortic pressure was generated with a transvalvular gradient of 14.9 +/- 7 mmHg (mean +/- SD). Regurgitation fraction ranged from 10 to 18% (mean 13.8 +/- 3%) in the best ring size. Valves with the best hemodynamic profile were used for implantation in three 70 kg pigs in an open chest model. The valve was collapsed in a 24 Fr catheter designed to allow slow, controlled release. After resection of the native leaflets, the new valve was placed in the subcoronary position. No additional sutures were used for securing the valve. Two animals were successfully weaned from cardiopulmonary bypass and maintained systemic pressures of 100/45 (+/-10) and 116/70 (+/-15) mmHg, respectively. Intraoperative color echocardiography revealed minimal regurgitation, central flow, full apposition of all leaflets, and no interference with coronary blood flow. Both animals were sacrificed after being off bypass for 2 hr. Postmortem examination revealed the valves to be securely anchored. The third animal was weaned from cardiopulmonary bypass but developed refractory ventricular fibrillation because of valve dislodgment due to structural failure. Although long term survival data are needed, development of a hemodynamically acceptable prosthetic aortic valve for transluminal placement is feasible.
Animals↗
Asymptomatic microembolism in patients with long-term ventricular assist support.
The incidence of clinically significant thromboembolic events is reported to be as high as 25% in patients with left ventricular assist devices (LVAD). Clinically detectable neurologic deficits resulting from thromboembolic events are reported to occur at a frequency of 0.0056% per patient-month with the Thermo Cardiosystems Heartmate 1000 (Woburn, MA) intraperitoneal LVAD (TCI). To date, the occurrence of asymptomatic cerebral microemboli in patients with this device has not been characterized. Transcranial doppler (TCD) monitorings were used for evaluation of the incidence of cerebral microembolism in 14 patients with the TCI LVAD. Studies were performed after LVAD support ranging from 7 to 305 days. Overall, 35 studies were obtained from the left middle cerebral artery for a duration of 30 minutes per study and the number of high intensity transient signals (HITS) were recorded. In one patient with a fatal stroke, an average of 0.86 HITS per study period (0.03/min) was observed. In 13 patients without any symptoms, an average of 0.46 HITS per study (0.016/min) was observed. Overall, no HITS were determined in 74% of the studies. Although the clinical significance or the nature of these microemboli is unknown, the data support that microembolism with the TCI LVAD is a rare event despite absence of anticoagulation. Long-term detailed neurocognitive testing and hematologic assessment is needed to establish the clinical relevance of these microemboli in patients with detected signals.
Adolescent↗