A juvenile sheep model for the long-term evaluation of stentless bioprostheses implanted as aortic root replacements.

BACKGROUND AND AIM OF THE STUDY: Orthotopic valve replacement in large animals is an important component of the preclinical assessment of bioprosthetic valves. To provide the most useful preclinical information, the development of models that parallel clinical practice patterns is essential. Therefore, we sought to develop a technically feasible and reproducible model for chronic evaluation of stentless bioprosthetic aortic valves implanted as aortic root replacements in juvenile sheep. METHODS: Juvenile domestic sheep (mean age 21+/-2.28 weeks; range: 17-26 weeks) underwent aortic root replacement using standard cardiopulmonary bypass (CPB) and surgical techniques. Animals were implanted with 19 mm (n = 21), 21 mm (n = 18) or 23 mm (n = 4) bioprostheses from two different manufacturers, and followed for 150 days. Animals surviving at least 150 days were considered long-term survivors; those which died prior to postoperative day (POD) 31 were considered operative deaths. RESULTS: Forty-three animals underwent aortic root replacement. The mean CPB time was 91+/-20 min (range: 62-149 min); mean cross-clamp time was 63+/-13 min (range: 39-95 min). Thirty-five animals (81%) survived the first 30 days of the study period. Five deaths occurred at POD 0 due to anastomotic complications. One death occurred each on POD 3, 6, and 26 as a result of prosthesis size mismatching, thromboembolic complications, and endocarditis, respectively. There were five late deaths. Twenty animals survived the minimum 150-day study period, and 12 were sacrificed at 183+/-17 days. Six animals remain alive at 151+/-0.98 days, and one animal died each on POD 184 and 190. The remaining 10 animals are not yet 150 days from their operation. Currently, all are well at 102+/-34 days (range: 33-140) days. CONCLUSION: These data suggest that long-term evaluation of stentless aortic bioprostheses implanted as aortic root replacements can be accomplished using juvenile sheep.

Anatomic study of the tricuspid valve in children.

We performed an anatomic study of the right atrioventricular valve in children under one year of age using a conservative method of dissection of the heart valve. The main aspects studied were the number of cusps and their morphometric characteristics, such as the width of the base and the depth of the cusps. Other parameters studied were the number of papillary muscles, number of tendinous cords, and diameter of the fibrous ring and the last one were divided in three regions, anterior, posterior and septal for localization of cusps. Our results showed that the number of cusps varied from two to four. Three cusps was the commonest finding and the fourth cusp, if present, was classified as anterolateral in location. The anterior and septal cusps had bases bigger than those of the posterior and anterolateral cusps; the septal cusp was deeper than the others; and the number of tendinous cords was greater for the anterior and septal cusps than for the posterior and anterolateral cusps. In addition, the posterior region showed great variability: in 35.7% it was occupied by undeveloped valve tissue and the posterior valve in these cases was located anteriorly.

Is the number of microembolic signals related to neurologic outcome in coronary bypass surgery?

Coronary artery bypass surgery (CABG) without cardiopulmonary bypass (CPB) may potentially reduce the number of microembolic signals (MES) associated with aortic manipulation or generated by the pump circuit, resulting in a better neurologic outcome after surgery. Our aim was to compare the frequency of MES and neurologic complications in CABG with and without CPB. Twenty patients eligible to routine CABG without CPB were randomized to surgery with CPB and without CPB and continuously monitored by transcranial Doppler. Neurologic examination was performed in all patients before and after surgery. The two groups were similar with respect to demographics, risk factors, grade of aortic atheromatous disease and number of grafts. The frequency of MES in the nonCPB group was considerably lower than in CPB patients, however, we did not observe any change in the neurologic examination during the early postoperative period. Neurologic complications after CABG may be related to the size and composition of MES rather than to their absolute numbers. A large prospective multicentric randomized trial may help to elucidate this complex issue.

Arterial wall damage caused by snaring of the coronary arteries during off-pump revascularization.

BACKGROUND: Anastomosis of a saphenous or mammary artery conduit to the coronary artery requires precise and reproducible microsurgical technique. Over the past 3 decades, the elective induction of cardiac arrest and circulatory support have provided the conditions suitable for microsurgical anastomosis to all coronary vessels. Beating heart coronary grafting was rejuvenated at our center in 1985 as an alternative to cardiopulmonary bypass and cardioplegic arrest. One of the requirements for off-pump grafting is local vascular control of the target vessel and prevention of bleeding into the field from the open coronary artery. The most common hemostasis technique in use today is the application of circumferential traction sutures and snares around the coronary artery. We performed a human cadaver study to evaluate the potential for local trauma to the native coronary artery caused by this method of hemostasis. METHODS: Our research team applied both 5-0 polypropylene and 2-0 polyester snares to the proximal and distal right coronary artery (RCA) and left anterior descending (LAD) in 25 isolated fresh human cadaver hearts. A total of 100 points of snare application to the native coronary vessels were induced and then investigated histologically, with hematoxylin-eosin, Weigert, and phosphotungstic hematoxylin staining. RESULTS: The results suggested a direct relationship between the severity of the arterial lesion induced by the snares and the degree of local atherosclerotic disease in the native coronary artery. Compression and buckling of the elastic lamellae with medial fractures (similar in nature to angioplasty but directed inward) were seen when snares were applied to a region with marked atherosclerotic disease. CONCLUSIONS: The application of snares to the coronary artery proximal and distal to the anastomotic site must be done with caution. In cases of marked atherosclerotic disease in the underlying coronary artery, a new intimal-medial lesion can occur with indiscriminate application of a tourniquet. This phenomenon may account for some of the reported cases of late peri-anastomotic or distal stenoses seen with off-pump coronary artery bypass grafting and significantly detract from the advantages offered by beating heart surgery. If one or both snares can be avoided entirely, or applied carefully to disease-free segments of the vessel, this problem may be avoided entirely.

Isquemia miocárdica intermitente após angioplastia cirúrgica do tronco de coronária esquerda / Intermittent myocardial isquemia after surgical angioplasty of the left main coronary artery

Dois pacientes do sexo masculino (38 e 53 anos) com angina estável, com estudo hemodinâmico revelando grave lesão de óstio de tronco de coronária esquerda (TCE), foram submetidos a angioplastia cirúrgica do TCE com patch de veia safena. Ao final da operação os pacientes apresentaram isquemia miocárdica intermitente, um deles com choque cardiogênico e, em ambos, reversão completa do quadro. O estudo hemodinâmico pós-operatório revelou adequada ampliação do TCE com função ventricular esquerda preservada nos dois pacientes. Embora a angioplastia cirúrgica do TCE seja uma alternativa técnica para os doentes com lesöes ostiais, chamamos a atenção para esta grave morbidade operatória, tendo como uma das possíveis causas o espasmo do TCE.

[Intermittent myocardial ischemia after surgical angioplasty of left main coronary artery]. / Isquemia miocárdica intermitente após angioplastia cirúrgica do tronco de coronária esquerda.

Two 38 and 53-year old male patients with unstable angina, whose hemodynamic study showed an isolated stenosis of the left coronary artery ostium, were submitted to a surgical angioplasty of the left main coronary artery (LMCA) with saphenous vein patch. At the end of the operation, the patients presented intermitent myocardial isquemia. One of them led to abrupt cardiogenic shock which reversed completely. The postoperative hemodynamic study demonstrated excellent left main coronary artery patency and normal left ventricular of LMCA has been proposed as an alternative technique to the treatment of ostial lesions, the surgical team should be prepared to face severe operative morbidity. The LMCA spasm has been considered as a possible etiology of that event.

Coronary artery bypass grafting without cardiopulmonary bypass through sternotomy and minimally invasive procedure.

Coronary artery bypass grafting without cardiopulmonary bypass (CPB) is now an accepted technique of myocardial revascularization in a special subset of patients. This paper presents our total experience in 1761 cases operated on since September 1981 until April 1997 out of a total of 9164 patients revascularized with the conventional technique during this period of time. Among the 1761 patients, 53 (3%) were operated on by minimally invasive surgery. The overall applicability was 19.2% and the most common grafted arteries were left anterior descending artery (LAD), right coronary artery (RCA), and diagonal. Results indicate that the operation can be performed with an acceptable mortality (2.3%) and that all types of arterial conduits can be used. The incidence of major postoperative complications were significantly lower in this group of patients when compared with our patients receiving conventional myocardial revascularization. Most importantly there was decrease cost when the procedure was used because no extracorporeal circulation cardioplegia sets or other cannulas were used. We conclude based on in this fifteen years experience that the technique of myocardial revascularization in a beating heart is justified, safe and can offer to selected patients the best option of coronary insufficiency surgical treatment.

Right internal thoracic artery through the transverse sinus in myocardial revascularization.

BACKGROUND: This study presents the late patency rate of the right internal thoracic artery (ITA) used in situ through the pericardium transverse sinus to the circumflex artery and its branches. METHODS: From April 1983 to December 1994, 2,642 patients were submitted to myocardial revascularization; 201 of them had bilateral ITAs. The right ITA through the transverse sinus was grafted to obtuse marginal artery in 170 patients (84.5%) and the left ITA was grafted to the anterior descending artery in 188 patients (93.5%). Angiographic studies were performed in 80 patients, 44 patients in the immediate postoperative period and 36 patients in the late follow-up (mean, 51.6 months). RESULTS: The right ITA was patent in 75 patients (93.7%) and the left ITA was patent in 77 (96.2%). At the late postoperative period, the right ITA was patent in 33 patients (91.6%) and the left ITA was patent in 34 (94.4%). CONCLUSIONS: The right ITA placed through the pericardium transverse sinus has a good long-term patency rate, similar to that observed with the left ITA and superior to that of saphenous vein grafts for myocardial revascularization.

Blood cardioplegia with warm reperfusion versus intermittent aortic crossclamping in myocardial revascularization. Randomized controlled trial.

To compare the efficiency of two methods of myocardial protection--blood cardioplegia and warm reperfusion with aspartate-glutamate enrichment of the solution versus intermittent aortic crossclamping--we randomized 60 patients for coronary artery bypass grafting. Hemodynamic parameters and hospital mortality were the end points. Pathologic antecedents and preoperative clinical conditions were similar in both group I (blood cardioplegia, 30 patients) and group II (aortic crossclamping, 30 patients). An average of 2.9 grafts per patient were performed in group I and 3.1 in group II. Duration of extracorporeal circulation was 100 +/- 28 minutes in group I and 85 +/- 23 minutes in group II (p < 0.05). The total time of aortic crossclamping was 62.8 +/- 24.5 minutes in group I and 44.3 +/- 14.9 minutes in group II (p < 0.05). There were comparable increases in cardiac index in group I and group II from the preoperative period to the first postoperative day, but none of these changes reached statistical significance. There were two deaths, one in the cardioplegia group (3.3%) and another in the intermittent aortic crossclamping group (3.3%). In conclusion, in myocardial revascularization, intermittent aortic crossclamping and blood cardioplegia with warm reperfusion enriched with aspartate-glutamate solution are methods of similar efficiency.

Anatomical study of the human tricuspid valve.

An anatomical study of the tricuspid valve was carried out in 50 human hearts of both female and male individuals using a method of dissection which preserves the integrity of the valve. Morphometric criteria such as area of cusp, width of cusp base, relation between commissure depth and cusp depth and morphological criteria such as the presence of atrioventricular cusp node, number of tendinous cords, perimeter of fibrous ring, and properties of papillary m. were adopted for characterization of a cusp. In 64% of cases, commissural cusps were present independent of the number of tricuspid cusps. The tricuspid valve was not consistently tricuspid, but was observed to present 2, 4, 5 or 6 cusps in 72% of cases.