Myocardial protection: the rebirth of potassium-based cardioplegia.
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The introduction of open-heart surgery more than 4 decades ago signaled a new era in medicine. For the 1st time, previously untreatable cardiac anomalies became amenable to surgical therapy. The use of the heart-lung machine seemed to grant the surgeon unlimited time in which to operate inside the heart. Still frustrated by poor operating conditions and the threat of air embolism, Denis Melrose introduced elective cardiac arrest in 1955. His use of a potassium citrate solution seemed to offer a safe method to effect a quiet, bloodless field. However, a few years after its inception, numerous reports began to question the safety of this approach, and the Melrose technique was abandoned in the early 1960s. Nearly 15 years elapsed before potassium-based cardioplegia regained popularity. During this period, topical hypothermia, coronary perfusion with intermittent aortic occlusion, and normothermic ischemia were evaluated and discarded. A few European investigators like Hoelscher, Bretschneider, and Kirsch had maintained their interest in chemical cardioplegia, and it was through their efforts that future researchers like Hearse and Gay spearheaded the return to potassium-based cardioplegia, which today forms the core of the cardiac surgeon's myocardial protective armamentarium and has contributed towards lowering operative mortality rates. (+info)
Urgent homograft aortic root replacement for aortic root abscess in infants and children.
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OBJECTIVE: To assess the results of early homograft aortic root replacement in infants and children with an aortic root abscess. DESIGN: Descriptive study of all patients with an aortic root abscess during 1987-97, identified by retrospective review of the echocardiographic and surgical registries. SETTING: A tertiary referral centre. PATIENTS: Five patients (age 0.6 to 13 years; two female) were identified with an aortic root abscess. Four had no known pre-existing congenital heart abnormality. Three had a misleading presentation and were referred to our hospital with non-cardiac diagnoses (fulminant hepatic failure; adult respiratory distress syndrome; cerebrovascular accident). The other two presented with septicaemia and a murmur, respectively. Blood cultures identified Staphylococcus aureus (n = 3) and Streptococcus pneumoniae (n = 2). Aortic root abscess was diagnosed by transthoracic echocardiography. INTERVENTIONS: Homograft aortic root replacement with coronary reimplantation was performed urgently (median one day after diagnosis). RESULTS: Four patients survived. The youngest died following multiorgan failure, multiple aortic fistulae, three valve involvement, and extensive tissue destruction preventing mitral valve replacement (S pneumoniae). Two of the four survivors have required further surgery: mitral valve replacement (0.3 years later), and pulmonary autograft replacement of the homograft (8.3 years later). All survivors remain in sinus rhythm and New York Heart Association functional class I. CONCLUSIONS: Infective endocarditis should be considered in any child with severe septicaemia or embolic phenomena. Echocardiographic diagnosis of an aortic root abscess indicates uncontrolled infection and impending haemodynamic collapse. Homograft aortic root replacement can be performed successfully in critically ill children with active infection. (+info)
Effects of leukocyte-depleted warm blood cardioplegia on cardiac and endothelial function.
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It has been reported that neutrophils and platelets have deleterious effects on myocardium and endothelium during and after ischemia. In this study we evaluated the effects of a leukocyte-depleting filter (Sepacell PLX, Asahi medical, Tokyo) during warm blood cardioplegia and early reperfusion on cardiac and endothelial function in the blood-perfused rat heart. Hearts (n = 7 per group) from donor rats were excised and perfused with blood at 37 degrees C from a support rat. After 10 min of stabilization, the hearts were arrested for 60 min with warm blood cardioplegia given at 20 min intervals. This was followed by 60 min of reperfusion. A leukocyte-depleting filter was used during the cardioplegia and the initial 10 min of reperfusion in the experimental group (Group F) and it was not used in the control group (Group N). Left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), maximum rate of left ventricular pressure rise (+dp/dt) and maximum rate of left ventricular pressure fall (-dp/dt) were measured as indices of left ventricular function before and after cardioplegic arrest. Coronary sinus effluent was obtained and the levels of MB isozyme of creatine kinase (CKMB), malondialdehide (MDA), elastase and thromboxane B2 (TXB2) were measured as indices of myocardial and endothelial injury. After 60 min of reperfusion, acetylcholine (Ach.) was administered to the coronary perfusate and the difference of nitric oxide (NO) concentration between inflow and outflow, and coronary blood flow were measured as an indication of endothelial function. Group F showed significantly lower LVEDP than Group N at 10 min of reperfusion. The elastase levels were significantly (p < 0.05) lower and the CKMB levels tended (p < 0.1) to be lower in Group F at 60 min of reperfusion. The administration of Ach. to the coronary perfusate showed significantly (p < 0.05) greater coronary blood flow and NO production in Group F. The results suggested that the use of a leukocyte-depleting filter during warm blood cardioplegia and early reperfusion preserves endothelial function and left ventricular diastolic compliance. The technique may provide beneficial effects by reducing reperfusion injury in patients undergoing cardiac surgery. (+info)
The effects of mannitol, albumin, and cardioplegia enhancers on 24-h rat heart preservation.
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During 24 h in vitro heart preservation and reperfusion, tissue damage occurs that seriously reduces cardiac function. Prevention of free radical production during preservation and reperfusion of ischemic tissue using free radical scavengers is of primary importance in maintaining optimal heart function in long-term preservation protocols. We examined whether mannitol (68 mM) and albumin (1.4 microM) in combination with other cardioplegia enhancers decreased free radical formation and edema and increased cardiac function during 24-h cold (5 degrees C) heart preservation and warm (37 degrees C) reperfusion in the Langendorff-isolated rat heart. The performance of mannitol-treated hearts was significantly decreased compared with that of hearts without mannitol treatment after 24 h of preservation with regard to recovery of diastolic pressure, contractility (+dP/dt), relaxation (-dP/dt), myocardial creatine kinase release, coronary flow, and lipid peroxidation. Albumin-treated hearts demonstrated higher cardiac function (contractility and coronary flow especially) than hearts not treated with albumin or hearts treated with mannitol, and this appears to be due to the positive effects of increased cellular metabolism and the enhancement of membrane stability. (+info)
Minimally invasive coronary surgery in women.
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OBJECTIVE: To evaluate the minimally invasive surgery in coronary artery bypass grafting and the feasibility for revascularization of triple vessel coronary artery disease. METHODS: Nine female patients, aged 49.1 to 81.6 years (mean 64.3), were operated on for triple vessel disease through minimally invasive surgical techniques. The surgeries were performed through limited left parasternal incision under femorofemoral extracorporeal circulation. The myocardium was protected by antegrade infusion of cold blood cardioplegic solution while the aorta was cross-clamped. Under direct vision, the left saphenous vein grafts were connected sequentially to the diagonal branch, obtuse marginal branch and posterior descending branch, and the left internal thoracic arterial graft was anastomosed to the left anterior descending artery in each patient. RESULTS: The number of distal anastomoses was 3 to 4 with a mean of 3.7. The aortic crossclamp time was 52 to 130 minutes (82 +/- 25 minutes). The duration of extracorporeal circulation was 78 to 151 minutes (115 +/- 29 minutes). The postoperative course was uneventful in all patients. The postoperative length of stay was 4 to 12 days (7.2 +/- 2.0 days). Follow-up (4.2 to 8.7 months, mean 6.4) was complete in all patients and there were no late deaths or angina. Coronary angiography of 2 patients showed patent grafts. All patients were satisfied with the good cosmetic healing of the incision. CONCLUSION: Our experience demonstrates that minimally invasive surgery in coronary artery bypass grafting is technically feasible and may be an alternative approach in surgical revascularization of triple vessel coronary artery disease, especially in female patients. (+info)
Extracardiac ablation of the canine atrioventricular junction by use of high-intensity focused ultrasound.
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BACKGROUND: High-intensity focused ultrasound has been applied to internal organs from outside the body to ablate tissue. No published study has assessed the feasibility of ablating cardiac tissue within the beating heart by use of this type of therapeutic ultrasound. The purpose of this study was to determine whether high-intensity focused ultrasound can be used to ablate the atrioventricular (AV) junction within the beating heart. METHODS AND RESULTS: Ten dogs were anesthetized and underwent a thoracotomy. The heart was covered with a polyvinyl chloride membrane. The thorax above the membrane was perfused with degassed water, which functioned as a coupling medium for the ultrasound. A 7.0-MHz diagnostic ultrasound probe was affixed to a spherically focused 1.4-MHz high-intensity focused ultrasound transducer with a 1.1x8.3-mm focal zone 63.5 mm from the ablation transducer. The diagnostic ultrasound probe was calibrated such that the location of the focal zone of the ablation transducer was identifiable on the 2-dimensional ultrasound image. Target sites were identified with the diagnostic ultrasound. The maximum ultrasound intensity for ablation (2.8 kW/cm2) was delivered to the AV junction only during electrical diastole and for a total of 30 seconds. Complete AV block was achieved in each of the 10 dogs with 6.5+/-5.6 (range, 3 to 21) 30-second applications of therapeutic ultrasound. Gross inspection showed that the mean lesion volume was 124+/-143 mm3, with a depth of 6.7+/-3.6 mm, a length of 5.7+/-2.5 mm, and a width of 4.7+/-1.8 mm. Four hours after the dogs were killed, histopathological study demonstrated a well-demarcated area of necrosis and early inflammation. CONCLUSIONS: High-intensity focused ultrasound produces well-demarcated lesions and appears to be a feasible energy source to create complete AV block within the beating heart without damaging the overlying or underlying cardiac tissue. This energy source may allow for a noninvasive approach to ablation of cardiac arrhythmias. (+info)
Atrial linear ablations in pigs. Chronic effects on atrial electrophysiology and pathology.
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BACKGROUND: Generation of long and continuous linear ablations is required in a growing number of atrial arrhythmias. However, deployment and assessment of these lesions may be difficult, and there are few data regarding their short- and long-term effects on atrial electrophysiology and pathology. METHODS AND RESULTS: A nonfluoroscopic mapping and navigation technique was used to generate 3-dimensional (3D) electroanatomic maps of the right atrium in 8 pigs. The catheter was then used to deliver sequential radiofrequency (RF) applications (power output gradually increased until 80% reduction in the amplitude of the unipolar electrogram) to generate a continuous lesion between the superior and inferior venae cavae. The animals were remapped 4 weeks after ablation during septal pacing. Lesion continuity was confirmed in all cases by the following criteria: (1) activation maps indicating conduction block [significant disparities in activation times (52.0+/-16.0 ms) and opposite orientation of the activation wave front on opposing sides of the lesion], (2) evidence of double potentials (interspike time difference of 52.3+/-17.1 ms), and (3) low peak-to-peak amplitude of the bipolar electrograms (0.7+/-0.6 mV) along the lesion. At autopsy, all lesions were continuous and transmural, averaged 50.5+/-6.7 mm, and were characterized histologically by transmural fibrosis throughout the length of the lesion. CONCLUSIONS: Long linear atrial ablation, created by sequential RF applications (using unipolar amplitude attenuation as the end point for energy delivery), results in long-term continuous and transmural lesions. Lesion continuity is associated with evidence of conduction block in the 3D activation maps and the presence of double potentials and low electrogram amplitude along the lesion. (+info)
Coronary vasoconstriction to endothelin-1 increases with age before and after ischaemia and reperfusion.
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OBJECTIVE: Ageing is known to be associated with changes within the heart. We investigated whether the coronary response to endothelin-1 (ET) and sarafotoxin S6c (S6c) is altered with increasing age, before and after cardioplegic arrest. METHODS: Using an isolated rat heart model, increasing concentrations of ET and S6c were administered to rats of different ages (group I = one month; group II = five months; group III = 21 months). An identical series of experiments was performed following the addition of indomethacin and NG-nitro-L-arginine methyl ester (L-NAME) to the Krebs perfusion fluid. In a third series of experiments, increasing doses of ET-1 were added to hearts following 4 h of cardioplegic arrest at 4 degrees C. RESULTS: Coronary flows are expressed as a percentage of initial coronary flow +/- SEM. There was a greater decrease in coronary flow in the older rats for all doses of ET-1. ET-1 (10(-9) M) reduced coronary flows to 72.8 +/- 3.7, 53.2 +/- 6.7 and 56.5 +/- 10.7% for groups I-III respectively (P = 0.01 I vs. II; P = 0.1 I vs. III). A similar response to ET-1 was seen in hearts perfused with indomethacin and L-NAME when compared to those perfused without (P = NS). Perfusion with ET-1 (10(-9) M) following 4 h of cardioplegic arrest reduced coronary flows to 40.5 +/- 4.9, 26.8 +/- 4.8 and 24.1 +/- 3.9%, respectively (P = 0.08 I vs. II; P = 0.03 I vs. III). Perfusion with S6c (10(-10) M) produced coronary flows of 93.3 +/- 5.5, 77.0 +/- 3.5 and 73.9 +/- 3.9% for groups I-III, respectively (P = 0.03 I vs. II; P = 0.01 I vs. III). Perfusion with S6c (10(-9) M) in the presence of L-NAME and indomethacin reduced coronary flows to 85.7 +/- 3.0, 81.6 +/- 2.2 and 74.6 +/- 3.6% (P = NS I vs. II; P = 0.03 I vs. III). CONCLUSIONS: The coronary vasoconstrictor response to ET-1 and S6c increases with age. The increased vasoconstriction in response to ET-1 is independent of the decrease in NO release seen with ageing. (+info)