Hugh S. Paterson

The development of small-diameter vascular grafts requires testing in large animal models before advancing to clinical trials. Vascular graft interposition implantation in sheep carotid arteries (CAs) is the most widely used model, but ovine CAs are prone to severe spasm following surgical manipulation, potentially impairing graft performance assessment. There is paucity in the literature on reducing sheep CA spasm using effective vasodilator therapeutic protocols. In this study, four healthy Merino cross White Suffolk wethers (1–2 years, 52.1 ± 0.8 kg) underwent CT angiography and CA graft surgery. CT angiography using iodinated contrast agent was performed with innominate artery access through the CA or ascending aortic arch access through the femoral artery. Sheep then underwent right CA sham surgery or left CA vascular graft implantation. A variety of vasodilators, including papaverine, sodium nitroprusside, verapamil, and their combination, were tested for preventing or treating CA spasms intraoperatively. Blood flow was reassessed immediately after CA surgery using CT angiography. The results showed that innominate artery access through the CA for CT angiography in sheep induced presurgical CA spasm with reduced arterial flow. Conversely, ascending aortic arch access through the femoral artery for CT angiography did not cause CA spasm and maintained arterial flow. During CA graft surgery, surgical trauma induced CA spasm, which was prevented by localized intra-arterial administration of vasodilators papaverine hydrochloride and verapamil before significant surgical manipulation.

Background: Three-dimensional intracardiac echocardiography (3D ICE) with wide azimuthal elevation is a novel technique performed for assessment of cardiac anatomy and guidance of intracardiac procedures, being able to provide unique views with good spatial and temporal resolution. Complications arising from this invasive procedure and the value of 3D ICE in the detection and diagnosis of acute cardiovascular pathology are not comprehensively described. This case illustrates a previously unreported iatrogenic complication of clot displacement from the intra-vascular sheath upon insertion of a 3D ICE catheter and the value of 3D ICE in immediate diagnosis of clot in transit through the heart with pulmonary embolism. Case presentation: We conducted a translational study of 3D ICE with wide azimuthal elevation to guide implantation of a left ventricular assist device (Impella CP®) in eight adult sheep. A large-bore 14 Fr central venous sheath was used to enable right atrial and right ventricular access for the intracardiac catheter. Insertion of the 3D ICE catheter was accompanied by a sudden severe cardiorespiratory deterioration in one animal. 3D ICE revealed a large highly mobile mass within the right heart chambers, determined to be a clot-in-transit. The diagnosis of pulmonary clot embolism resulting from the retrograde blood entry into the large-bore sheath introducer, rapid clot formation and consequent displacement into venous circulation by the ICE catheter was made. The sheep survived this life-threatening event following institution of cardiovascular support allowing completion of the primary research protocol. Conclusion: This report serves as a serious warning to the researchers and clinicians utilizing long large-bore sheath introducers for 3D ICE and illustrates the value of 3D ICE in detecting clot-in-transit within right heart chambers.

Lessons from the arterial revascularization trial

Composite arterial grafts using a T configuration from the left internal mammary artery (LIMA) are commonly used for coronary artery surgery. Little data exist regarding the use of saphenous vein (SV) in composite grafts from the LIMA. This study aimed to determine whether LIMA patency was reduced by the attachment of a SV T graft. Patients (N.=166) who underwent coronary bypass surgery using the LIMA for SV graft inflow were identified from a database. Post discharge angiography was performed for investigation of symptoms or evidence of myocardial ischemia. Follow-up identified episodes of angiography, re-intervention and death. Complete follow-up was obtained in 165 patients, mean 6 years (0-16 years). The mean patient age was 70 years and 43 patients underwent concomitant procedures. In 25 patients who underwent post discharge angiography, the LIMA and T anastomoses were widely patent in 14 patients. The SV graft was occluded at the T anastomosis in 8 patients and the distal limb of the LIMA was occluded in 2 patients. In no patients were the vein and LIMA both occluded. The use of the LIMA for SV graft inflow does not appear to compromise the LIMA graft even when SV graft occlusion occurs.