An experimental model of Stanford type B aortic dissection.

PURPOSE: To create an experimental model of aortic dissection with a long-lasting patent false lumen as a proper animal model for development of less-invasive treatment for aortic dissection. MATERIALS AND METHODS: Fifteen adult beagle dogs (weight, 10-12 kg) were used. The descending aorta was exposed by a left thoracotomy at the sixth intercostal space. The entry for the aortic dissection was created surgically just distal to the origin of the left innominate artery and the reentry was 5 cm distal to the entry point. Normal saline solution was injected into the aortic wall (ie, media) between these two points to create the dissection. The dogs were followed up at 1 day, 3 months, 1 year, and 2 years. RESULTS: All 12 surviving dogs had completely patent true and false lumina without any thrombi. Microscopic examination showed that the dissection was created in the tunica media layer, making it identical to aortic dissection in humans. Color Doppler imaging confirmed the patency of the true and false lumina and the relatively narrowed true lumen. CONCLUSION: In this canine model of aortic dissection, the false lumen has excellent long-term patency and the dissection plane is histologically similar to that in human aortic dissection. This model may contribute to the development of new treatments for Stanford type B aortic dissection.

Aortic valve-sparing operation and a total arch replacement by an elephant trunk method for Marfan's syndrome with aortic regurgitation and a DeBakey type IIIb dissection.

A 35 year-old male with Marfan's syndrome was referred with a fortuitous echographic finding of an abdominal aorta flap. Transthoracic echocardiography showed moderate aortic regurgitation and an aneurysm in the sinus of Valsalva. Computed tomography demonstrated an aneurysm in the sinus of Valsalva 60 mm in size and a DeBakey type IIIb dissection extending from the left subclavian artery to the right common iliac artery. An aortic valve-sparing operation (reimplantation), total aortic arch replacement and the elephant trunk method were used in this patient. An aortic valve-sparing operation is preferable because the patient is young, and has no need for anticoagulant therapy after surgery. The extent of the aortic reconstruction, including the intact aortic arch, was appropriate to prohibit future dilatation of the aortic arch and retrograde dissection from a DeBakey type IIIb dissection.

Surgical treatment of giant left atrium using a combined superior-transseptal approach.

We report on the usefulness of a combined superior-transseptal approach for the surgical treatment of giant left atrium. The posteroinferior wall and the roof of the left atrium were easily plicated and the mitral valve procedure was simple.

Autosynchronized systolic unloading during left ventricular assist with a centrifugal pump.

OBJECTIVES: The purpose of this study was to investigate how the inflow cannulation site of the left ventricular assist system with a centrifugal pump would influence cardiac function on failing heart models. METHODS: In 10 sheep, a left ventricular assist system was instituted by an outflow cannula in the descending aorta, two inflow cannulas in the left atrium and the left ventricle, and connecting those cannulas to a magnetically suspended centrifugal pump. A conductance catheter and a tipped micromanometer for monitoring the pressure-volume loop were also inserted into the left ventricle. Myocardial oxygen consumption was directly measured. Heart failure was induced by injection of microspheres into the left main coronary artery. The assist rate was varied from 0% to 100% at each inflow cannulation site. RESULTS: The pump flow with left ventricular cannulation increased during the systolic phase and decreased during the diastolic phase, whereas it was constant with left atrial cannulation. Ejection fraction with left atrial cannulation decreased as the assist rate increased, whereas that with left ventricular cannulation was maintained up to 75% assist. The external work with left atrial cannulation decreased gradually as the assist rate increased, whereas the external work with left ventricular cannulation did not decrease until the assist rate reached 75%. The myocardial oxygen consumption in both cannulations decreased proportionally as the assist rate increased; they were significantly less with left ventricular cannulation at the 100% assist rate than with left atrial cannulation. CONCLUSION: Left ventricular cannulation during left ventricular assistance maintains ejection fraction and effectively reduces oxygen consumption.

A rat model of ischemic cardiomyopathy for investigating left ventricular volume reduction surgery.

OBJECTIVE: The effects of volume reduction surgery (VRS) for ischemic cardiomyopathy are not fully understood. The development of a proper animal model will help to resolve this issue. METHODS: Study 1 (Noninvasive study): Twenty-six rats developed large akinetic left ventricular (LV) aneurysms or ischemic cardiomyopathy after anterior descending artery ligation (first surgery). Four weeks after the surgery, 13 rats underwent volume reduction surgery (second surgery) (VRS group), while 13 underwent rethoracotomy alone (sham group). Before the first surgery, and before and after the second surgery, the LV dimensions were measured by echocardiography, and the heart rate and systolic blood pressure were recorded by the tail cuff method. Study 2 (Invasive study): In 7 rats undergoing the VRS and 9 undergoing the sham operation, LV pressure was measured with a manometer-tipped catheter, immediately before and after the second surgery. RESULTS: Study 1: All rats survived the second surgery, after which LV end-diastolic diameter decreased and LV fractional shortening increased (both p < 0.001) in the VRS group. This group also increased heart rate after the second surgery (p < 0.05). Study 2: There were no differences in LV end-systolic or end-diastolic pressure between the two groups before and after the second surgery. CONCLUSIONS: This model enables reproducible physiological evaluation of the LV after VRS, and since the rats show postoperative survival, it provides a useful tool for various investigations.

A rat model of ischaemic or dilated cardiomyopathy for investigating left ventricular repair surgery.

1. The effects of left ventricular repair (LVR) surgery for ischaemic or dilated cardiomyopathy are not fully understood. The development of a proper animal model will help to resolve this issue. 2. The ischaemic cardiomyopathy (ICM) model used was as follows. Twenty-six rats developed ICM with a large akinetic left ventricular (LV) area after ligation of the left anterior descending artery (LAD). Four weeks after surgery, 13 rats underwent LVR by placating the akinetic area (LVR group), while 13 underwent rethoracotomy alone (sham group). 3. The dilated cardiomyopathy (DCM) model is as follows. Six Dahl salt-sensitive (DS) rats were fed an 8% NaCl diet from the age of 9 weeks and developed DCM. These rats had LVR by plicating the LV area between the papillary muscle bases (LVR group), while other rats underwent rethoracotomy alone (sham group). 4. Before LAD ligation in the ICM model or starting the high-salt diet in the DCM model and just before and after LVR or sham surgery, LV dimensions were measured by echocardiography and the heart rate and systolic blood pressure were recorded by the tail-cuff method. 5. In the ICM model, all rats survived the second surgery, after which LV end-diastolic diameter (EDD) decreased, LV fractional shortening (FS) increased (both P < 0.001 vs sham) and heart rate increased (P < 0.05) in the LVR group. 6. In the DCM model, LV EDD decreased and LV FS increased (both P < 0.001) in the LVR group. 7. Both models developed LV dilatation, tolerated LVR and enable reproducible physiological evaluation of the LV. Because the rats survived thereafter, both models may provide a useful tool for various investigations.