Nicola Vitale

Obstruction of Mechanical Mitral Prostheses: Analysis of Pathologic Findings

BACKGROUND The pathologic and echocardiographic findings observed in 87 patients with mitral valve obstruction were reviewed to ascertain the incidence of pannus formation versus that of thrombosis, the relationship between the two, and the time to the occurrence of pannus versus the time to thrombosis. METHODS Pannus morphology (concentric or eccentric), its location on the valve (atrial, ventricular, atrioventricular), and the presence and relationship of associated thrombi (atrial, ventricular, atrioventricular) were analyzed. The times between valve replacement and the occurrence of obstruction were also compared. RESULTS There were 10 caged-ball valves, 65 tilting-disc valves, and 12 bileaflet valves. Seventy-two patients underwent prosthetic replacement, and 15 underwent thrombolysis. Pannus alone was found in 27, pannus and thrombus in 39, and thrombus alone in 21. Primary thrombosis occurred earlier than pannus formation (p = 0.04); this was true for patients with bileaflet valves (p = 0.006) and those with tilting-disc valves (p = 0.04). Pannus was atrial in 19.7% (13/66), ventricular in 21.2% (14/66), and atrioventricular in 59.1% (39/66). Pannus morphology was concentric in 22.7% (15/66) and eccentric in 77.3% (51/66). Atrial secondary thrombi occur more often in patients with atrioventricular pannus (p = 0.04). Eight patients had reobstruction; this was caused by pannus formation in 5 and by thrombosis in 3. Five underwent reoperation, and 3 underwent thrombolysis. Reobstruction occurred earlier than the first event. CONCLUSIONS The frequency of pannus formation is much higher than that of thrombus formation, but thrombosis is of earlier onset than pannus formation. Thrombosis is due to the deposition of clots on the prosthesis, and a pannus occurs as the result of an inflammatory reaction developing on both valve surfaces.

Impact of competitive flow on wall shear stress in coronary surgery: computational fluid dynamics of a LIMA–LAD model

AIMS Competitive flow from native coronary vessels is considered a major factor in the failure of coronary bypass grafts. However, the pathophysiological effects are not fully understood. Low and oscillatory wall shear stress (WSS) is known to induce endothelial dysfunction and vascular disease, like atherosclerosis and intimal hyperplasia. The aim was to investigate the impact of competitive flow on WSS in mammary artery bypass grafts. METHODS AND RESULTS Using computational fluid dynamics, WSS was calculated in a left internal mammary artery (LIMA) graft to the left anterior descending artery in a three-dimensional in vivo porcine coronary artery bypass graft model. The following conditions were investigated: high competitive flow (non-significant coronary lesion), partial competitive flow (significant coronary lesion), and no competitive flow (totally occluded coronary vessel). Time-averaged WSS of LIMA at high, partial, and no competitive flow were 0.3-0.6, 0.6-3.0, and 0.9-3.0 Pa, respectively. Further, oscillatory WSS quantified as the oscillatory shear index (OSI) ranged from (maximum OSI = 0.5 equals zero net WSS) 0.15 to 0.35, <0.05, and <0.05, respectively. Thus, high competitive flow resulted in substantial oscillatory and low WSS. Moderate competitive flow resulted in WSS and OSI similar to the no competitive flow condition. CONCLUSION Graft flow is highly dependent on the degree of competitive flow. High competitive flow was found to produce unfavourable WSS consistent with endothelial dysfunction and subsequent graft narrowing and failure. Partial competitive flow, however, may be better tolerated as it was found to be similar to the ideal condition of no competitive flow.

Intraoperative color Doppler ultrasound assessment of LIMA-to-LAD anastomoses in off-pump coronary artery bypass grafting

BACKGROUND Although techniques for off-pump coronary artery bypass grafting (CABG) are continually being refined, angiographic follow-up studies have indicated a higher rate of anastomoses-related stenoses than expected after traditional on-pump CABG. This study was performed to evaluate the use of intraoperative epicardial color Doppler ultrasound to quality-assess left internal mammary artery (LIMA) to left anterior descending coronary artery (LAD) anastomoses performed on the beating heart. METHODS Twenty-four LIMA-to-LAD anastomoses were evaluated with real-time epicardial ultrasound imaging using an ultrasound transducer positioned between the paddles of the stabilizer during off-pump procedures. The length of the anastomosis (D(A)), diameters of LIMA (D(M)), LAD at the toe of the anastomosis (D1), and 5 mm distally to the anastomosis (D2) were measured, and the ratios between these variables were calculated. The flow velocity through the anastomoses was visualized by color Doppler coding, and flow was assessed with transit-time flowmetry. RESULTS The epicardial color Doppler ultrasound allowed accurate assessment of the anastomoses. Twenty-three (96%) of the primary anastomoses were confirmed as patent. Mean ratios of D1/D2, D(A)/D2, and D(M)/D2 were 0.89 +/- 0.13, 3.01 +/- 1.04 and 1.32 +/- 0.32, respectively. One anastomosis had a stenosis more than 50% detected by color Doppler ultrasound. After surgical revision, transit-time flow increased from 22 to 40 ml/min. CONCLUSIONS Intraoperative color Doppler ultrasound allowed adequate imaging for quality assessment of LIMA-to-LAD anastomoses performed on the beating heart. One anastomosis was revised due to a technical error detected by epicardial color Doppler imaging. Epicardial ultrasound scanning is a valuable tool for intraoperative assessment of LIMA-to-LAD anastomoses during off-pump coronary surgery.

Is unilateral antegrade cerebral perfusion equivalent to bilateral cerebral perfusion for patients undergoing aortic arch surgery

A best evidence topic in cardiothoracic surgery was written according to a structured protocol. The question addressed was whether unilateral antegrade cerebral perfusion is equivalent to bilateral cerebral plegia for cerebral protection during aortic arch surgery. Altogether 233 papers were found using the reported search, of which 17 presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these papers are tabulated. These papers documented antegrade selective cerebral perfusion in a total of 3548 patients: bilateral cerebral perfusion in 2949 patients and unilateral perfusion in 599 patients. Both methods of cerebral perfusion resulted in neurological injury rates of <5%, but the period of antegrade cerebral perfusion allowed by bilateral perfusion was significantly higher. While unilateral perfusion allowed around 30-50 min, bilateral perfusion allowed 86 to over 164 min of ASCP with an acceptably low CVA rate. Therefore, we conclude that while both methods are acceptable, once the ASCP time is expected to rise over 40-50 min, bilateral cerebral perfusion is the technique that is best documented to be safe.

Acetylsalicylic acid treatment until surgery reduces oxidative stress and inflammation in patients undergoing coronary artery bypass grafting

OBJECTIVES Acetylsalicylic acid (ASA) is a cornerstone in the treatment of coronary artery disease (CAD) due to its antiplatelet effect. Cessation of aspirin before coronary artery bypass grafting (CABG) is often recommended to avoid bleeding, but the practice is controversial because it is suggested to worsen the underlying CAD. The aims of the present prospective, randomized study were to assess if ASA administration until the day before CABG decreases the oxidative load through a reduction of inflammation and myocardial damage, compared with patients with preoperative discontinuation of ASA. METHODS Twenty patients scheduled for CABG were randomly assigned to either routine ASA-treatment (160 mg daily) until the time of surgery (ASA), or to ASA-withdrawal 7 days before surgery (No-ASA). Blood-samples were taken from a radial artery and coronary sinus, during and after surgery and analysed for 8-iso-prostaglandin (PG) F2α; a major F2-isoprostane, high-sensitivity C-reactive protein (hs-CRP), cytokines and troponin T. Left ventricle Tru-Cut biopsies were taken from viable myocardium close to the left anterior descending artery just after connection to cardiopulmonary bypass, and before cardioplegia were established for gene analysis (Illumina HT-12) and immunohistochemistry (CD45). RESULTS 8-Iso-PGF2α at baseline (t1) were 111 (277) pmol/l and 221 (490) pmol/l for ASA and No-ASA, respectively (P = 0.065). Area under the curve showed a significantly lower level in plasma concentration of 8-iso-PGF2α and hsCRP in the ASA group compared with the No-ASA group with (158 pM vs 297 pM, P = 0.035) and hsCRP (8.4 mg/l vs 10.1 mg/l, P = 0.013). All cytokines increased during surgery, but no significant differences between the two groups were observed. Nine genes (10 transcripts) were found with a false discovery rate (FDR) <0.1 between the ASA and No-ASA groups. CONCLUSIONS Continued ASA treatment until the time of CABG reduced oxidative and inflammatory responses. Also, a likely beneficial effect upon myocardial injury was noticed. Although none of the genes known to be involved in oxidative stress or inflammation took a different expression in myocardial tissue, the genetic analysis showed interesting differences in the mRNA level. Further research in this field is necessary to understand the role of the genes.

Different graft flow patterns due to competitive flow or stenosis in the coronary anastomosis assessed by transit-time flowmetry in a porcine model,

OBJECTIVE To assess whether coronary graft flow patterns are affected differently by native coronary competitive flow or by stenosis of the coronary anastomosis. METHODS Nine pigs (65-70 kg) underwent off-pump grafting of the left internal mammary artery to the left anterior descending artery (LAD). Transit-time flow patterns in the mammary grafts were recorded under four different conditions: (1) baseline flow (proximal LAD occluded), (2) full competitive flow, (3) partial competitive flow and (4) after creation of a stenosis in the anastomosis. Competitive flow was achieved by an adjustable occluder on the left anterior descending artery. The mean luminal stenosis of the anastomosis was 75+/-11%, calculated by epicardial ultrasound. Mean flow, systolic and diastolic antegrade and retrograde flow during different flow conditions were calculated as ratios of baseline flow and compared. Different derived flow indexes were calculated and compared in the same manner. Friedmans test and post hoc analyses by Wilcoxon signed-ranks were performed without correction for multiple comparisons. RESULTS Mean graft flow was more reduced by competitive flow than by a stenotic anastomosis of 75+/-11%. Competitive flow significantly decreased diastolic antegrade flow and both diastolic and systolic maximum peak flows, but increased retrograde flow, compared with baseline and stenosis. Furthermore, competitive flow and stenosis could be distinguished by analysis of several derived indexes. Pulsatility index (maximum-minimum flow/mean flow) and insufficiency percent (retrograde flow as fraction of total flow) was increased significantly more by competitive flow than by stenosis. Diastolic filling percent was significantly reduced at competitive flow compared with stenosis and baseline. CONCLUSIONS The mammary graft flow was significantly reduced by native coronary competitive flow, but marginally decreased by a stenotic anastomosis of 75% mean luminal stenosis. Reduction of graft flow due to competition was particularly evident in diastole. A detailed flow pattern analysis may differentiate between competitive flow and stenosis of the anastomosis.

Epicardial Colour-Doppler Scanning of Coronary Artery Stenoses and Graft Anastomoses

Objective : Epicardial ultrasound scanning was applied during coronary surgery to assess coronary artery stenoses and quality of distal graft anastomoses, with special emphasis to the left anterior descending artery (LAD). Design : Twenty-three patients with coronary artery disease (M:F 19:4, mean age 65.0 - 9.5 years) had coronary artery bypass grafting (CABG) on cardiopulmonary bypass. Intraoperative scanning of coronary artery stenoses and graft anastomoses was performed with a new 10 MHz linear array Vingmed transducer connected to a GE Vingmed System FiVe echocardiography unit. Coronary stenoses detected by ultrasound were compared with preoperative angiograms. Intraoperatively, coronary graft flow was assessed with a Medi-Stim transit-time flowmeter. Results : Twenty LADs were investigated. In 17 LADs (85%) stenoses were clearly identified. In three LADs (15%) stenoses were not identified because LADs were deeply intramyocardial or the stenosis was very proximal. There was a significant correlation between LAD stenoses detected by ultrasound and angiogram ( R = 0.7; p < 0.01). Mean number of grafts was 3.8 - 0.9. Of 26 LAD anastomoses assessed, good images were obtained in 22 cases (84.4%); the mean LAD diameter measured 1 cm below the anastomosis was 1.6 - 0.2 mm. In two LADs images were rated fair and in two LADs images were poor because of intramyocardial LAD. No technical error of the anastomoses was detected. All grafts had good flows as ascertained by flow measurements. Conclusion : Epicardial ultrasound scanning with the new 10 MHz transducer allowed satisfactory imaging of coronary stenoses and graft anastomoses. Factors limiting the quality of imaging are proximal lesions, intramyocardial vessel, vessel tortuosity, and extensive calcifications. Epicardial ultrasound scanning with updated technology should become a further advancement to graft assessment during off-pump coronary surgery.

Anticoagulation for prosthetic heart valves during pregnancy: the importance of warfarin daily dose

We read with great interest the case by Leyh and associates on prosthetic valvular thrombosis in a pregnant patient anticoagulated with low-molecular-weight heparin (LMWH) [1]. Their case confirms once more the inefficacy of heparins to protect the mother from prosthetic valve thrombosis during pregnancy [2]. The usual management of anticoagulation in pregnant women is stopping warfarin administration and replacing it with either unfractioned or LMW heparin on the basis that warfarin has many untoward effects on the fetus [2]. According to our experience the untoward effects of warfarin are dose-dependent [3]. In our study 43 pregnant patients with mechanical valve prostheses were kept on warfarin continuously until the 38th week of gestation when a cesarean section was planned after warfarin administration had been stopped for 2 days. Patients were divided into two groups according to the daily warfarin intake ð.5 mg or # 5 mg); we found a significant increase in the number of fetal complications in the group of patients taking daily doses of warfarin . 5 mg. We observed a total of two prosthetic valve thromboses. In detail in the group of 33 gestations, with patients taking a warfarin dose # 5 mg, there were 28 healthy babies and only five fetal complications (four spontaneous abortion and one fetal growth retardation). In the other group of 25 gestations, with patients taking a warfarin dose. 5 mg, three fullterm pregnancies and 22 fetal complications (18 spontaneous abortions, one stillbirth, one ventricular septal defect and two warfarin embriopathies) were observed. Furthermore, there was a very significant correlation between warfarin daily dose and fetal complications. The explanation for these findings is that warfarin has a molecular weight of approximately 1000 and readily cross the placenta to the fetus. The mother may therefore be within anticoagulation therapeutic range, but the fetus is considerably overdosed because of immature liver enzyme systems and low levels of vitamin K-dependent clotting factors [4]. These findings may confidently suggest a clinical approach to these patients. Those patients whose warfarin intake is # 5 mg with an international normalized ratio (INR) within therapeutic range may continue to take warfarin during the entire pregnancy under strict medical surveillance, and consider a programmed cesarean section at the 38th week of gestation while briefly interrupting warfarin therapy. If the patients prefer to have vaginal delivery, heparin over the last 2 weeks of gestation should be offered as an option. On the other hand, those patients whose warfarin doses are . 5 mg should be made fully aware of a likely much higher risk of fetal complications during pregnancy. If they decide to carry on pregnancy with warfarin and a have a bileaflet or an aortic valve prosthesis, the INR range may be lowered to 2.0–2.5 with the aim of bringing the warfarin intake down to 5 mg while still reaching a satisfactory antithrombotic effect. In those women who choose not to take warfarin and are at higher thrombotic risk (mitral prostheses, atrial fibrillation, first generation valves, previous thromboembolism), inhospital heparin treatment, at least between weeks 6 and 12 and 2 weeks before delivery, seems justified. It would have been very interesting to know the daily dose of warfarin of the patient treated by Leyh et al. to find out whether she would have benefited from warfarin administration during pregnancy. In pregnant patients with mechanical valves warfarin at a daily dose # 5 mg seems to be the drug that provides the best antithrombotic effect with a reasonably low rate of untoward fetal complications.

Midterm evaluation of the Sorin Bicarbon heart valve prosthesis: single-center experience

BACKGROUND The purpose of this study was to perform midterm evaluation of the clinical performance of the Sorin Bicarbon mechanical heart valve prosthesis. METHODS From November 1992 to December 2002, 328 patients underwent isolated aortic (AVR; 156) or mitral (MVR; 172) valve replacement with the Sorin Bicarbon mechanical valve. Concomitant surgery was performed in 83 patients (25.2%). RESULTS Total hospital mortality was 5.2%. Survival at 7 years was 79.5% for AVR and 82.4% for MVR. Kaplan-Meier freedoms from valve-related complications were as follows: thromboembolism 92.7% (AVR 94.8%, MVR 92.1%); bleeding 93% (AVR 91.9%, MVR 94.5%); nonstructural dysfunction 96.6% (AVR 94.7%; MVR 97.9%); endocarditis 97.7% (AVR 97.4%, MVR 98.1%); and reoperation 95.7% (AVR 96.6%, MVR 93.9%). Overall freedom from valve-related death was 93.2% (AVR 99.3%, MVR 91.2%). At the end of follow-up, 88.9% of survivors were in New York Heart Association class I or II. CONCLUSIONS The Sorin Bicarbon valve is a satisfactory mechanical valve prosthesis with low mortality and morbidity and good functional results.

Prosthetic valve obstruction: thrombolysis versus operation: Updated in 2000

As Originally Published in 1994: Figure options Download full-size image Download as PowerPoint slide