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PubMed2005

Myocardial perfusion monitoring during coronary artery bypass using an electrocardiogram-triggered laser Doppler technique.

Electrocardiogram (ECG)-triggered laser Doppler perfusion monitoring (LDPM) was used to assess myocardial perfusion, with minimum myocardial tissue motion influence, during coronary artery bypass grafting (CABG). Thirteen subjects were investigated at six phases: pre- and post-CABG; post aorta cross-clamping; pre and post left internal mammary artery (LIMA) graft declamping; and post aorta declamping. The perfusion signal was calculated in late systole and late diastole, with expected minimum tissue motion, and compared with arrested heart measurements. Patient conditions or artifacts caused by surgical activity made it impossible to perform and analyse data in all six phases for some patients. No significant (n = 5) difference between perfusion signals pre- and post-CABG was found. Diastolic perfusion signal levels were significantly (p < 0.02) lower compared with systolic levels. After aorta cross-clamping, the signal level was almost zero. A distinct perfusion signal increase after LIMA and aorta declamping, compared with pre-LIMA declamping, was found in ten cases out of 13. A significantly (p < 0.04) lower perfusion signal in the arrested heart compared with in the beating heart was registered. Influence from mechanical ventilation was observed in 14 measurements out of 17. In conclusion, ECG-triggered LDPM can be used to assess myocardial perfusion during CABG. Perfusion signals were lower in the arrested heart compared with in the beating heart and in late diastole compared with late systole. No significant difference between pre- and post-CABG was found.

Adult↗
PubMed1982

Effect of the pH of cardioplegic solution on postarrest myocardial preservation.

The assumption that an alkaline cardioplegic solution is advantageous to the arrested heart is not supported by experimental evidence. Three groups of dogs were subjected to 2 hours of hypothermic arrest using a potassium cardioplegic solution of varying pH: group 1 (n = 8), pH 7.1; group 2 (n = 6), pH 7.4; and group 3 (n = 8), pH 7.7. Left ventricular (LV) function curves were obtained before arrest and after reperfusion, and the percent recovery of LV function was calculated. Coronary blood flow (CBF), oxygen and lactate use, and adenosine triphosphate and creatine phosphate were measured before and after arrest. Recovery of LV function was 83 +/- 4% (mean +/- SEM) in group 1 and 75 +/- 6% in group 2. LV function in group 3 was significantly depressed at 51 +/- 5% (p less than 0.01). Immediately after arrest, CBF and oxygen consumption were lowest in group 1 and highest in group 3 (p less than 0.01). CBF increased 23 +/- 9% in group 1, 110 +/- 29% in group 2 and 277 +/- 33% in group 3. Oxygen consumption was 2.2 +/- 0.4 vol/100 g/min in group 1, 3.63 +/- 0.5 vol/100 g/min in group 2 and 4.63 +/- 0.7 vol/100 g/min in group 3. All groups showed postarrest depression of adenosine triphosphate and creatine phosphate, but return of creatine phosphate to control was slowest in group 1 (p less than 0.01). These results indicate no advantage to an alkaline cardioplegic solution and suggest that an acidic cardioplegic solution, by inhibiting metabolism, may increase protection of the arrested heart.

Adenosine Triphosphate↗
PubMed1994

Feasibility of intraoperative coronary angiography during hypothermic cardioplegic arrest.

Although intraoperative coronary angioplasty has the potential to enhance revascularization in selected patients undergoing coronary bypass, this technique is only rarely performed, due in part to the lack of angiographic monitoring. Accordingly, to develop angiographic techniques potentially applicable to intraoperative angioplasty, 6 conditioned dogs were placed on full cardiopulmonary bypass, the aorta was cross-clamped, and the heart arrested with cold cardioplegia solution. After 45 minutes of arrest, selective coronary angiography was performed employing catheters introduced through a proximal aortotomy. Small-volume contrast injections resulted in excellent opacification; however, the contrast agent stagnated within the coronary tree. Fortunately, intracoronary flush injection of the saline-cardioplegia solution resulted in immediate and complete contrast washout. After discontinuation of bypass, echocardiography revealed normal left and right ventricular function. Histopathologic analysis of tissue specimens from animals in which contrast was flushed documented the presence of normal coronary arteries and myocardium. These findings demonstrate methods by which intraoperative coronary angiography can be performed in the arrested heart without having adverse effects on either the cardiac function or histologic appearance. These techniques may have application for the performance of intraoperative angioplasty.

Animals↗
PubMedDate not supplied

[Characteristics of the activation of lysosomal enzymes in the rat liver after death and during resuscitation].

Alterations in activity of lysosomal acid phosphatase and cathepsin D, as well as of hepatocyte ultrastructure were studied in rat liver tissue after experimental heart arrest within 10 and 30 min and during the early post-resuscitation period. Cathepsin D free activity in a supernatant fraction as well as both enzymatic activities in lysosomal fraction were increased after 30 min heart arrest. Activity of acid phosphatase and cathepsin D in lysosomes was decreased, while the activity of the free enzymes was increased within 1 and 4 hrs after resuscitation. Triton X-100 (0.025%) caused labilization of lysosomal membranes. Alterations in ultrastructure of hepatocytes were observed within 30 min of the heart arrest and within first hour of the post-resuscitation period. The lysosomal membranes tended to normalization within 24 hrs after the post-resuscitation period, whereas the enzymatic activity remained elevated. Role of lysosomes in regulation of intracellular metabolism is discussed.

Acid Phosphatase↗
PubMed1995

Pathways of Rb+ influx and their relation to intracellular [Na+] in the perfused rat heart. A 87Rb and 23Na NMR study.

The aims of this study were to characterize the routes of influx of the K+ congener, Rb+, into cardiac cells in the perfused rat heart and to evaluate their links to the intracellular Na+ concentration ([Na+]i) using 87Rb and 23Na nuclear magnetic resonance (NMR) spectroscopy. The rate constant for Rb+ equilibration in the extracellular space was 8.5 times higher than that for the intracellular space. The sensitivity of the rate of Rb+ accumulation in the intracellular space of the perfused rat heart to the inhibitors of the K+ and Na+ transport systems has been analyzed. The Rb+ influx rates were measured in both beating and arrested hearts: both procaine (5 mmol/L) and lidocaine (1 mmol/L) halved the Rb+ influx rate. In procaine-arrested hearts, the Na+,K(+)-ATPase inhibitor ouabain (0.6 mmol/L) decreased Rb+ influx by 76 +/- 24% relative to that observed in untreated but arrested hearts. Rb+ uptake was insensitive to the K+ channel blocker 4-aminopyridine (1 mmol/L). The inhibitor of Na+/K+/2 Cl- cotransport bumetanide (30 mumol/L) decreased Rb+ uptake only slightly (by 9 +/- 8%). Rb+ uptake was dependent on [Na+]i: it increased by 58 +/- 34% when [Na+]i was increased with the Na+ ionophore monensin (1 mumol/L) and decreased by 48 +/- 9% when [Na+]i was decreased by the Na+ channel blockers procaine and lidocaine. Dimethylamiloride (15 to 20 mumol/L), an inhibitor of the Na+/H+ exchanger, slightly reduced [Na+]i and Rb+ entry into the cardiomyocytes (by 15 +/- 5%). 31P NMR spectroscopy was used to monitor the energetic state and intracellular pH (pHi) in a parallel series of hearts. Treatment of the hearts with lidocaine, 4-aminopyridine, dimethylamiloride, or bumetanide for 15 to 20 minutes at the same concentrations as used for the Rb+ and Na+ experiments did not markedly affect the levels of the phosphate metabolites or pHi. These data show that under normal physiological conditions, Rb+ influx occurs mainly through Na+,K(+)-ATPase; the contribution of the Na+/K+/2 Cl- cotransporter and K+ channels to Rb+ influx is small. The correlation between Rb+ influx and [Na+bdi during infusion of drugs that affect [Na+]i indicates that, in rat hearts at 37 degrees C, Rb+ influx can serve as a measure of Na+ influx. We estimate that, at normothermia, at least 50% of the Na+ entry into beating cardiac cells is provided by the Na+ channels, with only minor contributions (< 15%) from the Na+/K+/2 Cl- cotransporter and the Na+/H+ exchanger.

Animals↗
PubMed1991

The relevance of coronary sinus interventions in cardiac surgery.

The concept of arterialization of the coronary venous system was first discussed almost 100 years ago. Subsequently, those attracted by this approach have chosen the coronary veins as an alternative route for interventional and surgical therapy. Modern techniques of coronary sinus interventions (CSI) have been suggested mainly for temporary support and protection of ischemic myocardium. Based on the dense meshwork structure of the venous vasculature, CSI may be effective even in the presence of serious coronary artery disease. Three major techniques have been suggested for different indications in cardiology and cardiac surgery: 1) ECG-synchronized retroperfusion of arterial blood, which is supposed to positively affect ischemic myocardium by phasic supply of oxygen to deprived areas mainly in cardiac emergencies, 2) retroinfusion of cardioplegia in the arrested heart, which is now a well-established clinical technique, and 3) intermittent coronary sinus occlusion during antegrade cardioplegic delivery in the arrested heart and in the early reperfusion period after surgical revascularization, or in cardiac emergencies. The beneficial effect of pressure-controlled intermittent coronary sinus occlusion is assumed to result from cyclic occlusion and release of the coronary sinus shifting venous blood to underperfused regions, thereby facilitating substrate delivery and subsequent washout of metabolites. Experimental studies and first clinical trials suggest that all methods of CSI are safe and feasible, and the ultimate goals of reduction of infarct size and preservation of jeopardized ischemic myocardium will be achieved.

Cardiac Catheterization↗
PubMed1989

Hyperkalemic cardiac arrest, prolonged heart massage and simultaneous hemodialysis.

A 53 year old diabetic patient underwent CABG and aortic valve replacement in another institution and developed postoperative oliguric and hyperkalemic acute renal failure. Shortly after transferring to our unit a cardiac arrest occurred. Immediate resuscitative measures were ineffective. The serum potassium level was 10.2 mmol/l. Conventional arteriovenous hemodialysis was initiated while the patient was still undergoing cardiac massage. When the serum potassium level was lowered to 6.5 mmol/l, 90 min later, the heart began to beat. After hemodialysis was discontinued the patient was reactive and fully conscious. The use of simultaneous hemodialysis with prolonged mechanical heart massage as a reliable method for recovery in hyperkalemic cardiac standstill is stressed.

Acute Kidney Injury↗
PubMed2004

Initial experience with beating-heart single valve replacement surgery at the University Hospital of the West Indies, Kingston, Jamaica.

The objective of this study was to examine the consequences of performing single cardiac valve replacement procedures utilizing a beating-heart technique on typical patients presenting to the cardiothoracic surgery service for aortic or mitral valve replacement. Beating heart aortic (4) or mitral valve (1) replacement was performed on patients from July 2000 to November 2002. A stratified sample of five patients who underwent standard arrested-heart single valve replacement procedures between April 1997 and November 2002 was selected for retrospective comparison with the beating-heart group. Operative and post-operative variables were compared between the two groups of patients and subjected to statistical analysis. There was no statistical difference between the two groups with respect to age, pre- or post-operative New York Heart Association (NYHA) scores, cardiopulmonary bypass time, aortic cross-clamp time, intra-operative blood transfusion, or post-operative hospital stay. Post-operatively, in the beating heart group, ventilation time, mediastinal blood loss and requirements for inotropic drugs were significantly reduced (p = 0.0054), p = 0.0019 and 0 = 0.02 respectively) compared to the arrested-heart group. Single cardiac valve replacement surgery utilizing a beating heart technique may offer benefits to patients over traditional arrested-heart surgery. Post-operative blood loss, inotrope requirements and ventilation times are significantly reduced, possibly resulting in better recovery and potentially fewer complications in the post-operative period. There may be cost benefits, important in the context of healthcare delivery in developing nations. These early results suggest the need for a regional prospective randomized trial to compare beating-heart single valve replacement surgery with traditional techniques.

Adult↗
PubMed1992

Capillary length, tortuosity, and spacing in rat myocardium during cardiac cycle.

Microvascular geometry was evaluated in rat left ventricular midmyocardium (male Sprague-Dawley, n = 14), arrested in systole (S) or diastole (D), by bolus injections of CaCl2 or KCl, respectively. The histological method employed in this study allowed for the visualization of capillary pathways from arteriole to venule. Capillary length, as directly measured from terminal arteriole to collecting venule, was not significantly different between S and D groups, averaging 606 +/- 15 microns (pooled mean +/- SE). The capillary length tortuosity, defined as the ratio of the capillary length to the direct arteriovenous distance, was significantly increased in systolic-arrested hearts (S = 1.31 +/- 0.03; D = 1.18 +/- 0.02, P < 0.01). At the level of individual capillary segments, however, there was no increase in tortuosity in systolic-arrested hearts (S = 1.17 +/- 0.03; D = 1.16 +/- 0.02). Intercapillary spacing was significantly more uniform in systolic-arrested hearts. These data suggest that in systole, capillary length and tortuosity are generally preserved, and capillary spacing is more uniform, serving to maintain geometric conditions for oxygen supply during the cardiac cycle.

Animals↗
PubMed2001

Electroplegia: an alternative to blood cardioplegia for arresting the heart during conventional (on-pump) cardiac operation.

BACKGROUND: Aortic cross-clamping is contraindicated in patients with severe atherosclerosis of the ascending aorta, and administration of chemical cardioplegia may be cumbersome in these patients. In this study, we demonstrate an alternative method of achieving cardioplegia by electrical stimulation of the vagus nerve. METHODS: In anesthetized canines, the left anterior descending coronary artery was reversibly ligated for 90 minutes, followed by cardiopulmonary bypass (CPB) and randomization to three groups (n = 8 each): (1) BCP group: 1 hour of intermittent hypothermic (4 degrees C) blood cardioplegia infusion; (2) CPB group: 1 hour of CPB alone; (3) EP group (group receiving electroplegia): 1 hour of intermittent vagal stimulation (total of 60 20-second electrical stimuli at 40 Hz, 6 to 10 V) with adjunctive pyridostigmine (0.5 mg/kg), verapamil (50 microg/kg), and propranolol (80 microg/kg) to potentiate hyperpolarization and suppress ectopic escape beats. RESULTS: The EP group achieved consistent intervals of arrest with 3.8 +/- 1.2 escape beats per 20-second stimulation period. After 2 hours of reperfusion off CPB, the left anterior descending coronary artery segmental shortening was reduced from baseline in all groups, but the segmental shortening recovered to a greater extent in the EP group than in either the CPB or BCP group (2.4% +/- 1.4% versus -1.3% +/- 1.3% versus -4.0% +/- 0.8%, p < 0.05). Infarct size (TTC stain, percentage of area at risk) was comparable among groups (EP: 20.9% +/- 4.7%; CPB: 29.6% +/- 3.2%; BCP: 25.1% +/- 5.7%). Postischemic left anterior descending coronary artery endothelial function (percent maximum relaxation to acetylcholine) was depressed in the EP group (68.6% +/- 7.6% versus 102.3% +/- 6.4%, p < 0.05), but was comparable versus nonischemic circumflex function in the BCP group (77.1% +/- 11.9% versus 100.4% +/- 10.0%, p = 0.15) and the CPB group (93.8% +/- 6.6% versus 93.3% +/- 6.6%). CONCLUSIONS: Electroplegia achieves elective intermittent cardiac arrest, avoids hypothermia, chemical cardioplegia, and aortic cross-clamping, with physiological outcomes comparable to blood cardioplegia.

Acetylcholine↗
PubMed2001

Myocardial protection with pinacidil induced hyperpolarized arrest during cardiopulmonary bypass.

OBJECTIVE: To investigate the myocardial protective effects of pinacidil-induced hyperpolarized arrest and compare with those afforded by conventional depolarized hyperkalemic arrest. METHODS: Eighteen dogs were equally divided into three groups: normothermic hyperpolarized group (Group A), hypothermic hyperpolarized group (Group B), and hyperkalemic group (Group C). Pinacidil (50 mumol/L) containing 37 degrees C St. Thomas solution (K+ 5 mmol/L, 10 ml/kg), pinacidil (50 mumol/L, Sigma, USA) containing 4 degrees C St. Thomas solution (K+ 5 mmol/L, 10 ml/kg) and 4 degrees C standard St. Thomas solution (K+ 16 mmol/L, 10 ml/kg) were infused respectively through the aortic root after aortic-clamping. Heart arrest and its recovery, ultrastructure of the myocardium, the level of serum myocardial enzymes, and lipid peroxide and adenine nucleotide of the myocardium were measured. Hemodynamics during ischemia and after reperfusion were observed. RESULTS: The percentages of normal mitochondria and glycogen did not change much during ischemia (except at 60 min) and after reperfusion in B Group, but declined markedly in Group C 30 min and 60 min after ischemia and 20 min after reperfusion (P < 0.01). In Group A, they were lower than those of Group B before ischemia, but higher than those of Group C. The recoveries of CO, SV, CI, LVSW, RVSW and MAP in Group B were significantly better than those in other two groups 15 min and 30 min after reperfusion (P < 0.05 and 0.01, respectively). However, they were still better in Group A than those in Group C (P < 0.05 and 0.01, respectively). The onset of heart arrest was faster in Groups C and B than that in Group A. Highly elevated serum myocardial enzymes were observed 60 min after ischemia and 20 min after reperfusion in Group C, while they were only mild in the hyperpolarized groups, especially in Group B, and their recoveries were rapid. Adenine nucleotides of the myocardium were better preserved in Group B than in other two groups 30 min, 60 min after ischemia, and 20 min after reperfusion (P < 0.05 and 0.01, respectively). They were also much better in Group A than in Group C (P < 0.05 and 0.01, respectively). Lipid peroxide of the myocardium were significantly lower in Group B than in other groups 20 min after reperfusion (P < 0.01), and they were lower in Group A than in Group C (P < 0.05). CONCLUSIONS: Myocardial protection for global ischemia during cardiopulmonary bypass (CPB) could be achieved with hyperpolarized heart arrest induced by pinacidil, an ATP-sensitive potassium channel opener, especially in the hypothermic state. The protection is weaker in normothermia but is still superior to that with traditional depolarized hyperkalemic arrest.

Adenine Nucleotides↗
PubMed2003

Sutureless robot-assisted mitral valve repair: an animal model.

BACKGROUND: Robotic mitral valve repair with the da Vinci robotic surgical system has been performed in more than 70 patients at our institution. This procedure reduces the need for blood transfusions, shortens hospital stay, and hastens return to normal activities. However, the robot-assisted repair also requires longer cardiopulmonary bypass and arrested-heart times than conventional open repairs. Because of increased risk of myocardial damage, arrhythmia, and other significant morbidities associated with longer arrested-heart time, a more efficient tissue approximation and adherence technique was evaluated to reduce operating time. METHODS: Twelve Dorset sheep were divided equally into 2 groups. In the control group Cosgrove-Edwards annuloplasty bands were secured to the posterior annulus with conventional 2-0 Ticron mattress sutures placed with robotic assistance. In the experimental group, the band was secured with double-armed nitinol U-clips placed with robotic assistance. Postoperative echocardiography was used to assess mitral valve function, and the animals were sacrificed at 3 or 6 months for histological evaluation. RESULTS: Total U-clip placement time was significantly decreased at 2.6 +/- 0.2 (mean +/- SEM) minutes versus total suture placement time at 4.9 +/- 0.4 minutes (P =.001). The main difference in time occurred between clip deployment at 0.75 +/- 0.1 minutes and suture tying at 2.78 +/- 0.2 minutes (P =.000003). Pathologic review showed excellent band incorporation at 3 and 6 months. Echocardiographic imaging showed no discernible mitral valve stenosis or regurgitation. CONCLUSIONS: With more cardiac procedures progressing toward minimally invasive approaches, novel technology to improve existing techniques must be evaluated. Nitinol U-clips help to reduce arrested-heart time and may improve outcome by decreasing morbidity. U-clip placement is intuitive, easily learned, and effective in securing the annuloplasty band to the mitral annulus.

Animals↗