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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The QRS complex in lead V5 was studied during cardiac surgery. R wave amplitude decreased after induction of anesthesia to approximately 50% to 60% of the preanesthetic level before the institution of CPB (P < 0.001). An rS complex appeared immediately after cardioversion and changed in configuration to an Rs complex 15 to 30 minutes after aortic declamping. The R wave continued to recover toward the preanesthetic level at sternal closure. Patients with coronary artery disease had a poorer recovery of the R wave (P < 0.05) than patients with valvular heart disease; the former recovered to only 50% of the preanesthetic level at sternal closure. Nonsurvivors had much smaller R waves (26.1 +/- 20.5%) than survivors (P < 0.001). The R wave peaked 30 to 40 ms after initiation of the QRS complex, which indicates recovery of conductivity and the activation sequence of the left ventricular (LV) free wall, which is easily disturbed by hypothermia, cardioplegia, and ischemia during aortic cross-clamping. Monitoring QRS complex changes in lead V5 appears to be important on weaning from cardiopulmonary bypass to detect regional ischemia, and also to observe electrophysiologic recovery of the LV free wall.
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PMID:QRS complex changes in the V5 ECG lead during cardiac surgery. 147 59

A study was designed to quantify the influence of the Hemopump on myocardial metabolism in regional myocardial ischemias induced by repetitive balloon-occlusions (3.5 minutes) of the LAD in 12 sheep (b.w. 49-61 kg). In order to make immediate comparisons and obtain paired-couples, ischemias were carried out with and without the Hemopump in operation. An energetic unloading of the left ventricle was achieved by the Hemopump already under preocclusion conditions, reducing myocardial O2-consumption from 7.52 to 5.98 ml/min/100 g LV (= 20%) as well as lowering the LVEDP from 13.3 to 9.8 mmHg (p less than or equal to 0.01). During ischemia a clear increase of LVEDP (13.3 to 21.0 mmHg) occurs, which was prevented in the group with Hemopump-assist (9.8 to 12.1 mmHg). Combined with a sustained higher diastolic aortic pressure, a better myocardial perfusion pressure resulted. Energetic unloading and improvement of perfusion conditions might be the cause of the significantly lowered release of lactate and potassium. Due to theses fibrillation (n = 3) only occurred during occlusions without Hemopump-support. In summary, a significant reduction of the ischemic burden on the myocardium was found. Thus the Hemopump could be of benefit to patients who fail to be weaned from CPB or who are suffering from instable cardiovascular performance.
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PMID:Myocardial support and protection during regional myocardial ischemia using the Hemopump assist device. 178 11

The ability to measure ATP synthesis rates using 31P-NMR spectroscopy is demonstrated in the normal, ischemic, and postischemic myocardium in vivo. Cardiopulmonary bypass (CBP) was employed to induce 20 min of global myocardial ischemia, and to conduct magnetization transfer measurements during the ischemic episode and following reperfusion and return to normal circulation. For the first few minutes of ischemia, transfer of magnetization from ATP gamma to Pi was extensive and the resultant fractional reduction (delta M/M0) in the Pi resonance intensity reached approximately 100%. Subsequent to reperfusion and stabilization off CPB and on normal circulation, both the fractional reduction and the spin-lattice relaxation time, T1*, of the Pi resonance were determined when ATP gamma spins were saturated. Under these conditions, the unidirectional ATP synthesis rate was 0.41 +/- 0.09 (SEM, N = 4) mumol/s/g wet wt. The data suggest that in the canine myocardium in vivo, glycolytic enzymes mediate a very rapid exchange between Pi and ATP gamma-phosphates during early phases of ischemia; in the postischemic reperfused myocardium, however, the glycolytic contribution to the unidirectional Pi----ATP rate measured by NMR in vivo is relatively small compared to that observed in glucose-perfused, postischemic rat hearts.
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PMID:Measurement of ATP synthesis rates by 31P-NMR spectroscopy in the intact myocardium in vivo. 237 2

Protective effect of aprotinin pretreatment was assessed by functional, biochemical and morphological preservation in four hour global ischemia followed by one hour reperfusion in dogs. Cardioplegia was induced by intermittent infusion of cold Mg-lidocaine solution. Aprotinin 10,000 KIU/kg was given in low dose group (8 dogs), and 20,000 KIU/kg in high dose group (6 dogs); one half was given before ischemia and another half during ischemia. Betamethasone, coenzyme Q and nifedipine were also given equally in both groups before ischemia. Results were as follows: 1. Four (50%) of low dose group and all of high dose group were successfully taken off CPB and survived for one hour reperfusion. 2. High dose group showed significantly higher blood pressure and LVSWI than low dose group after one hour reperfusion (p less than 0.05). 3. Serum N-acetyl-beta-D-glucosaminidase and mitochondrial aspartate aminotransferase showed the significantly lower activity in high dose group than in low dose group after one hour reperfusion (p less than 0.05). There was no significant difference in the activities of serum beta-glucuronidase and MB-creatine kinase. 4. Myocardial tissues, excised after one hour reperfusion, contained significantly higher creatine phosphate in high dose group than in low dose group (p less than 0.05). There was no significant difference in the contents of adenosine triphosphate, calcium and water. 5. Severely injured mitochondrion were significantly lesser in high dose group than in low dose group. All lysosomes showed mild swelling or enlargement, but those membranous structures were well-preserved in both groups. In conclusion, aprotinin pretreatment might be effective in myocardial protection against prolonged global ischemia, by inhibiting the "leak out" of lysosomal enzymes.
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PMID:[Improved myocardial protection by aprotinin pretreatment in prolonged global ischemia]. 248 66

Myocardial protection by the Hamburg oxygenated crystalloid cardioplegic solution was evaluated. A prospective metabolic study was conducted by measuring the myocardial adenosine triphosphate (ATP) and creatine phosphate (CP) contents by enzymatic techniques in 30 coronary bypass patients with a mean of 3.5 (+/- 0.9) aorto-coronary bypass grafts. Mean aortic cross clamp time was 48.4 (+/- 9.8) min. Myocardial samples were obtained from the left anterolateral ventricular wall: 1 = before CPB, 2 = before aortic cross clamp removal, 3 = 10 min following reperfusion. During ischemia, there was no statistically significant decrease in myocardial ATP contents [3.26 (+/- 0.82) vs 3.01 (+/- 0.92) mumol/g of frozen weight]; in contrast myocardial CP contents decreased significantly [2.71 (+/- 1.44) vs 1.87 (+/- 1.19) mumol/g; p = 0.01]. Following 10 min of reperfusion, the mean ATP level [2.96 (+/- 0.84) mumol/g] was 90% of the preischemic value, and myocardial CP levels (2.32 (+/- 0.92) mumol/g] increased to 85% of preischemic levels. Spontaneous myocardial defibrillation was observed in 93.3% of cases. Early postischemic myocardial function was studied in 228 cardiac operations using the same myocardial protection. 48 patients underwent multiple valve replacement (MUVR), and 180 patients had 4 or more aorto-coronary bypass grafts (CABG). Spontaneous myocardial defibrillation was observed in 90.3% of all; cases; mean CPB time after aortic cross clamp removal was 10.3 (+/- 8) min. Cardiac index by Swan-Ganz thermodilution catheter were measured just before cardiopulmonary bypass and one and twelve hours later.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Clinical and metabolic evaluation of myocardial protection by oxygenated cardioplegia (Hamburg solution) in multiple coronary bypass surgery or polyvalvular replacement]. 258 99

Many studies have demonstrated fairly high incidence of supraventricular arrhythmias after coronary artery bypass surgery, and have tried to identify preoperative, operative and postoperative factors related to their appearance. The present paper analysed 186 patients submitted to coronary artery bypass and reported a incidence of atrial fibrillation of 6.04% (11 cases). The male sex was dominant (81.2%) with ages varying from 49 to 73 (mean 54.58) years. The preoperative incidence of diabetes, smoking and systemic hypertension were, respectively, 18.2%, 54.51% and 36.4%. The mean number of vessels bypassed was 2.42 +/- 1.19 and the left circumflex artery was involved in 81.20% of these cases. Cardiopulmonary bypass time was 100 +/- 39.6 min and ischemic arrest time of 79.6 +/- 37.7 min. Single double stage cannulae for venous drainage were used in 45.5% of the patients and ventricular fibrillation and cardiac overdistention occurred in 63.60% immediately after CPB. Atrial fibrillation presented around 1.66 +/- 2.17 days in the postoperative period and 45.5% of the patients had more than one distinct episode of the arrhythmia. Treatment constituted of cardioversion in 25%, atenolol oral in 18.75% and digitalis associated to quinidine in 56.25%. These numbers permit us to suggest that some of the above factors may contribute to the genesis of arrhythmias, such as single double stage cannulation for venous drainage, inadequate myocardial protection, overdistention and cardiac fibrillation and, mainly, the presence of proximal circumflex artery obstructions responsible for atrial ischemia before and during surgery.
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PMID:[Postoperative atrial fibrillation in myocardial revascularization]. 281 36

Twenty-five patients undergoing aortic valve replacement were administered two different electrolyte solutions pre- and intraoperatively: patients in group A (n = 9) received a balanced solution of electrolytes and trace metals with aspartate as anion (Inzolen), patients in group B (n = 16) received Ringer's solution with potassium chloride referenced to frequently-measured serum potassium levels. From the left ventricular apex region, needle biopsies were obtained at three points in time: 1. beginning of CPB, 2. end of ischemia, 3. after ten minutes of reperfusion. The tissue samples were enzymatically analyzed for the content of ATP, CP, ADP and lactate. In group A (patients with aspartate) ATP (moderately) and CP (markedly) decreased after ischemia with a marked increase after reperfusion. ADP and lactate in this group (A) increased at the end of ischemia and decreased after reperfusion. ATP and CP in group B (KCl) showed a similar course during the investigation. Lactate (markedly) and ADP (moderately) increased after ischemia without changing after reperfusion. Mean values of ATP and CP in group A were significantly higher than those of group B at all times. Mean values of ADP and lactate, however, in group A were below those of group B. The data indicate an improvement in energetic metabolism of myocardium in man. The results point out the possible importance of aspartates in compound with electrolytes and trace metals in preservation of biochemical energy.
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PMID:[Effect of aspartate compounds on the biochemical characteristics of myocardial energy metabolism in man]. 666 81

Previous studies show that (1) hypoxemia depletes immature myocardium of amino acid substrates and their replenishment improves ischemic tolerance, (2) reoxygenation on cardiopulmonary bypass causes oxygen-mediated damage without added ischemia, and (3) this damage may be related to the nitric oxide-L-arginine pathway that is affected by amino acid metabolism. This study tests the hypothesis that priming the cardiopulmonary bypass circuit with glutamate and aspartate limits reoxygenation damage. Of 22 immature Duroc-Yorkshire piglets (< 3 weeks old), five were observed over a 5-hour period (control), and five others underwent 30 minutes of CPB without hypoxemia (cardiopulmonary bypass control). Twelve others became hypoxemic by reducing ventilator inspired oxygen fraction to 6% to 7% (oxygen tension about 25 mm Hg) before reoxygenation on cardiopulmonary bypass for 30 minutes. Of these five were untreated (no treatment), and the cardiopulmonary bypass circuit was primed with 5 mmol/L glutamate and aspartate in seven others (treatment). Left ventricular function before and after bypass was measured by inscribing pressure-volume loops (end-systolic elastance). Myocardial conjugated diene levels were measured to detect lipid peroxidation, and antioxidant reserve capacity was tested by incubating cardiac muscle with the oxidant t-butylhydroperoxide to determine the susceptibility to subsequent oxidant injury. CPB (no hypoxemia) allowed complete functional recovery without changing conjugated dienes and antioxidant reserve capacity, whereas reoxygenation injury developed in untreated hearts. This was characterized by reduced contractility (elastance end-systolic recovered only 37% +/- 8%*), increased conjugated diene levels (1.3 +/- 0.1 vs 0.7 +/- 0.1*), and decreased antioxidant reserve capacity (910 +/- 59 vs 471 +/- 30 malondialdehyde nmol/g protein at 2 mmol/L t-butylhydroperoxide*). In contrast, priming the cardiopulmonary bypass circuit with glutamate and aspartate resulted in significantly better left ventricular functional recovery (75% +/- 8% vs 37% +/- 8%*), minimal conjugated diene production (0.8 +/- 0.1 vs 1.3 +/- 0.1*), and improved antioxidant reserve capacity (726 +/- 27 vs 910 +/- 59 malondialdehyde nmol/g protein*) (*p < 0.05 vs cardiopulmonary bypass control). We conclude that reoxygenation of immature hypoxemic piglets by the initiation of cardiopulmonary bypass causes myocardial dysfunction, lipid peroxidation, and reduced tolerance to oxidant stress, which may increase vulnerability to subsequent ischemia (i.e., aortic crossclamping). These data suggest that supplementing the prime of cardiopulmonary bypass circuit with glutamate and aspartate may reduce these deleterious consequences of reoxygenation.
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PMID:Studies of hypoxemic/reoxygenation injury: without aortic clamping. VIII. Counteraction of oxidant damage by exogenous glutamate and aspartate. 747 74

Alteration of normal blood flow to the heart may result in myocardial ischemia or infarction. Perfluorochemical emulsions offer a potential means to improve oxygenation of the heart during periods of hypoxia. The small particle size and linear disassociation curve of perfluorochemicals may result in greater oxygen delivery than blood particularly in severely diseased or damaged atherosclerotic vessels. Intracoronary Fluosol given during PTCA reduces the myocardial ischemia which occurs during balloon inflation. Although Fluosol does not prevent myocardial dysfunction during prolonged balloon inflations, new concentrated perfluorochemicals have increased oxygen delivery capacity and may have greater benefit. Experimentally, during coronary occlusions, perfluorochemicals promote higher oxygen tension in areas of ischemia and result in infarct size reduction. Reduction of oxygen free radicals has been proposed as the mechanism by which Fluosol exerts its ability to reduce infarct size. Clinical studies with Fluosol and thrombolytic therapy for treatment of acute myocardial infarctions are ongoing to assess ability to preserve myocardial function. Perfluorochemical cardioplegia can deliver oxygen during periods of cardiac arrest and may improve immediate post CPB myocardial function particularly in those patients with pre-existing left ventricular dysfunction. The oxygen-carrying capacity of perfluorocarbons and its unique properties offer great advantages to improve the treatment of cardiovascular diseases.
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PMID:Cardiovascular applications of fluorocarbons: current status and future direction--a critical clinical appraisal. 784 11

Current knowledge suggests that risks of glucose-containing solutions for patients undergoing CPB are hypothetical at best. Instead, patients may benefit from reduced perioperative fluid requirements bestowed by intraoperative glucose-containing solutions. This risk-benefit analysis does not apply to patients undergoing circulatory arrest. This population endures the certain risk of global CNS ischemia; furthermore, no studies address the effect of glucose on fluid requirements in this population. As the benefit of glucose during operations requiring circulatory arrest is unknown and the probable risk of exacerbating global CNS is high, deliberate hyperglycemia in this population is probably unwise. For patients undergoing CPB without circulatory arrest, the risk-benefit balance falls in favor of adding glucose. The contention that hyperglycemia worsens CNS deficits after cardiac operation is undocumented and may not be true. For their patients undergoing CPB, clinicians should seriously consider using glucose-containing priming solutions.
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PMID:Pro: glucose priming solutions should be used for cardiopulmonary bypass. 854 68


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