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Left heart bypass is typically established by left atrial appendage cannulation. We report a technique using inferior pulmonary vein cannulation, which is technically simpler. We have used this technique in 20 cases with reliable venous inflow.
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BACKGROUND: Partial left heart bypass is widely used in the repair of traumatic aortic disruptions. We recently encountered two patients with posterior circulation infarctions after repair of traumatic aortic disruptions using heparin-less partial left heart bypass. METHODS/RESULTS: Both patients underwent interposition graft repair of thoracic aortic transections at the level of the isthmus. The first patient developed a left posterior inferior cerebellar artery infarct after a clamp time of 44 minutes. Swelling of this infarct necessitated ventriculostomy placement. The second patient developed a pontine infarct postoperatively after a cross-clamp time of 56 minutes and suffered a persistent left upper extremity paresis. CONCLUSIONS: Partial left heart bypass may have predisposed these two patients to clamp-related embolic events via the left vertebral artery. This experience warrants further surveillance to detect these infarcts which can require neurosurgical intervention. Additionally, the events suggest reconsideration of systemic anticoagulation during aortic cross-clamp times exceeding 30 minutes.
Partial left-heart bypass provides circulatory support and distal perfusion for repair of thoracic and thoracoabdominal aortic disease without requiring full anticoagulation. Unfortunately some patients, such as those with significant lung contusion in the setting of trauma or those with severe chronic obstructive pulmonary disease and degenerative aneurysms, do not tolerate single-lung ventilation. We have recently modified our left-heart bypass circuit in selected cases to provide supplementary oxygenation, making this technique more broadly applicable.
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During partial left heart bypass (LHBP), the flow delivered by an assist device is easy to measure while residual left ventricular function (LVI) seems difficult to assess. In this study, we have attempted to define the separate right and left ventricular function during LHBP. In 6 anesthetized dogs, following thoracotomy and systemic heparinization, aorta and left atrium were cannulated and connected to the servo-controlled roller pump (modified Stöckert-System). Following saline infusion (30 ml/kg), LHBP was started and maintained at 50 ml/min/kg throughout 6 h. Standard hemodynamic parameters were continuously monitored. Cardiac output, blood gas analyses, hemoglobin and activated coagulation time were measured at regular intervals. LVI was calculated as the difference between cardiac output and assist-flow rate. Other derived variables were obtained using standard formulas. The Wilcoxon rank-test was used for the statistical analysis. The results, as median and 25th-75th percentile, are summarized in the graphics 1-6. Under the experimental conditions of this study, the flow performance and stroke work of the right ventricle remained unchanged, while the work-unloaded left ventricle maintained only a part of systemic perfusion. Neglecting the physiological shunt and its changes, which influences the difference between the left and right ventricular output, the simple formula to assess LVI during LHBP seems plausible.
For introduction of a left atrial (LA) cannula by the transseptal puncture technique, we examined the feasibility of using biplane transesophageal echocardiography (B-TEE). A transseptal puncture was performed on 15 patients (3 male; 12 female; mean age, 48.9 +/- 11.2 years) by B-TEE guide during percutaneous transvenous mitral comissurotomy (PTMC). The entire Brocken-brough needle and the position of its tip were clearly observed in the right atrium by a longitudinal image of B-TEE in all patients (100%), and in 2 (13%) of them also by the transverse image of B-TEE. The puncture was about 1 cm caudal from the center of the fossa ovalis to avoid any large residual atrial septal defect. After transseptal puncture, a Mullin's sheath (7 Fr) and a dilator (14 Fr) were inserted into the left atrium in order, and then an Inoue's balloon catheter (12 Fr) was introduced without difficulty into the left atrium in all patients. With contrast injection, the position of the sheaths's tip was clearly confirmed by B-TEE. Left heart bypass support (left atrial-femoral artery bypass or AAB) was performed on 2 patients after percutaneous introduction of the LA cannula using this technique, and both were successfully supported and survived. With B-TEE guidance, the Brockenbrough atrial septal puncture and introduction of the LA cannula into left atrium can be performed easily. Thus, percutaneous left heart bypass can be set up quickly and safely even in an intensive care unit or outpatient emergency room without radiographic guidance.
Preservation of the donor heart is an important and controversial subject in heart transplantation. The donor's heart function must be maintained at the most viable state possible. This study examined the effectiveness of LHB in cases of brain death and clarified the possibility of this application for donors as a bridge to heart transplantation. Changes in hemodynamic parameters and histological findings in brain-dead dogs were studied. Two groups of brain-dead dogs were involved in this study: group L (n = 10) as a LHB support and group C (n = 10) as a control. Brain death was induced by an ethanol injection into the subdural space of the dogs. This condition was maintained with volume replacement and dobutamine administration (5 micrograms/kg/ min). In group L, LHB that was achieved with a transaortic valve left ventricular drainage cannula inserted from a carotid artery and return via a femoral artery cannula was performed after brain death. A Bio-pump was utilized for the kind of assist device. Left ventricular output assist ratio averaged 60%. The parameters of left ventricular function (Max. dp/dt, Emax) at the time of brain death deteriorated by about 70%. In group L, they could keep this level over the 6-hr study period. On the other hand, the Emax value at 3 hours and the Max. dp/dt value at 4 hours decreased significantly when compared to the time of brain death (0-hr) for group C. At the 6-hr study period, histological findings showed only minimal change in the myocardium with slightly interstitial edema in group L. On the other hand, severe ischemic change in the myocardium with many contraction bands was found in group C. This data suggests that LHB is effective to preserve heart function in cases of brain death. This application may make it possible to maintain the viability of other organs by maintaining circulatory blood flow and pressure.
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Explore the source record for details and available documents.
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