Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.11.18 (MAP)
 7,412 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied reflex responses to pressure changes at arterial and cardiopulmonary baroreceptors in five awake dogs with atrioventricular block before and after baroreceptor denervation. We changed ventricular pacing rate and blood volume to vary cardiac output and arterial (MAP) and central venous pressure (CVP). We determined peripheral resistance (TPR) and atrial rate (HRA) as responses. In the intact animal, regression analysis showed an average relationship across dogs of TPR = 169-0.69 MAP-1.952 CVP + error. Correlation (r) between observed and predicted TPR was 0.83. For HRA, regression indicated HRA = 291.66-2.319 MAP + 8.144 CVP + error (r = 0.899). TPR and MAP are percent of control at 90 beats/min; CVP is in mmHg; HRA, in beats/min. Although its coefficient is smaller, MAP explains approximately 69% of the variation in TPR. After arterial baroreceptor denervation, effects of MAP on TPR were insignificant and the coefficient for CVP increased. Subsequent vagal block eliminated all reflex responses. Effects from the two receptor sites sum linearly. They act cooperatively with changes in blood volume, but oppose one another with cardiac output changes.
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PMID:Cardiovascular control by arterial and cardiopulmonary baroreceptors in awake dogs with atrioventricular block. 260 88

The hemodynamic effects of verapamil pretreatment versus no pretreatment were evaluated in five acutely hyperkalemic dogs. Using ECG evidence for severe hyperkalemia, the halothane-anesthetized dogs were rendered acutely hyperkalemic to similar plasma levels of K+ (K+ = 8.2 +/- 0.8 mEq/l verapamil plus hyperkalemia, K+ = 9.4 +/- 0.2 mEq/l hyperkalemic controls). The verapamil-hyperkalemic group had significantly lower cardiac indexes (CI) (CI = 1.3 +/- 0.5 1 X min-1 X m-2 verapamil plus hyperkalemia vs. CI = 3.0 +/- 0.2 1 X min-1 X m-2 hyperkalemic controls) and lower mean arterial pressures (MAP = 60 +/- 13 mmHg verapamil plus hyperkalemia vs. MAP = 96 +/- 7 mmHg hyperkalemic controls). Calcium therapy for hyperkalemia that returned CI to control levels in hyperkalemic controls only partially reversed the severe hemodynamic depression and did not improve the AV block seen during hyperkalemia in the presence of the calcium entry blocker verapamil. Surprisingly, the total mEq of KCl infused at the same rate into verapamil-pretreated dogs to result in similar high serum potassium levels was only one-third that required in dogs not pretreated with verapamil (1.6 +/- 0.3 mEq/kg KCl in verapamil-hyperkalemia group vs. 5.0 +/- 0.7 mEq/kg KCl in hyperkalemic controls).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Verapamil worsens rate of development and hemodynamic effects of acute hyperkalemia in halothane-anesthetized dogs: effects of calcium therapy. 642 14

We have described the value of the diastolic slope of the MAP recording at the end of a pacing train as a qualifying marker for the induction of delayed afterdepolarization (DAD) dependent arrhythmias. In the present study (1) the behavior of the slope at different time points during a pacing train was quantified and related to the arrhythmogenic outcome (group A) and (2) termination of DAD dependent VT was related to changes in the slope steepness (group B). In dogs with chronic complete AV block, a MAP was recorded during (1) ventricular pacing, before and after ouabain administration (group A) and (2) 6 spontaneous and 6 lidocaine induced VT terminations (group B). During control (group A), the slope at the end of pacing train was 5 +/- 3 m V/s (mean +/- SD), independent of the pacing duration. During ouabain, this increased to 20 +/- 15 mV/s (P < 0.05), varying with the duration of pacing. The slope was steeper after pacing for 4 seconds, compared to 20 seconds (26 +/- 12 mV/s vs 16 +/- 13 mV/s, P < 0.05) which corresponded with more frequent VT induction. In spontaneously terminating VTs (group B), CL increased from 353 +/- 54 ms at the start to 434 +/- 78 ms (P < 0.05) before VT termination. This corresponded with a decreasing steepness of the slope from 19 +/- 10 mV/s to 6 +/- 5 mV/s (P < 0.05). In lidocaine induced VT termination, the CL and the steepness of the slope showed an identical behavior. There is a dynamic variation in the steepness of the diastolic slope during pacing, which depends on the duration of pacing and predicts arrhythmogenic outcome. Furthermore, a decrease in steepness of the slope during DAD dependent VT can be used to predict VT termination.
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PMID:The dynamic behavior of the diastolic slope of monophasic action potential can be related to the occurrence and maintenance of delayed afterdepolarization dependent arrhythmias. 999 Jun

Normally, ventricular APD exceeds the VERP. However, under specific circumstances this relation may change and can become inverse. This phenomenon of postrepolarization refractoriness may be caused by a decrease in excitability. The threshold current (TC) for pacing has never been quantified as a possible explanation for these observations. Using a MAP pacing catheter in the right ventricular apex, the rate dependent behavior of TC, VERP, and APD before and after procainamide (dose 20 mg/kg in 10 min + 5 mg/min infusion) was determined in 17 dogs with chronic complete AV block. Initially, TC was determined with 0.1 mA accuracy. Using a pacing current of at least twice TC, VERP and APD showed a similar, rate dependent shortening for PCLs 800, 575, and 350 ms. Procainamide treatment led to an equal, rate independent VERP and APD increase: no post repolarization refractoriness. Subsequently, accuracy for TC determination was increased to 0.01 mA. Comparing PCLs 800 and 250 ms, TC doubled from 0.05 +/- 0.01 to 0.10 +/- 0.09 mA during control and almost tripled from 0.06 +/- 0.02 to 0.17 +/- 0.10 mA (P < 0.05) after procainamide. Using a fixed pacing current of exactly twice TC found at 800 ms PCL during control, VERP exceeded APD after procainamide treatment at 300 and 250 ms PCL: postrepolarization refractoriness. Increasing the pacing current to twice the rate dependent TC, the relation between VERP and APD normalized: no postrepolarization refractoriness. We conclude that after procainamide, rate dependent TC increase is of major importance for the phenomenon of postrepolarization refractoriness.
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PMID:Rate dependent effects of procainamide on the threshold current for pacing in the setting of postrepolarization refractoriness in dogs. 1008 43

To examine the surgical indications and the results of the maze procedure, we reviewed 30 cases who underwent the maze procedure concomitantly with other open heart surgery from October 1995 to October 1997.: the average age was 60.9 years (37 to 75 years) and mean follow up period was 12.3 months (1 to 25 months). The modified maze procedure described by Kosakai and associates was applied in all patients. Twenty one patients (72.4%) regained atrial rhythm and eight patients (27.6%) sustained atrial fibrillation in the follow up periods. The left atrial diameter measured by echocardiography and cardiothoracic ratio were significantly larger in the latter group of patients, compared with those who recovered normal sinus rhythm (63.8 +/- 19.5 versus 51.2 +/- 7.8 mm and 67.7 +/- 8.1 versus 59.2 +/- 5.4%). In order to perform the combined maze procedure, cardiac arrest time and cardiopulmonary bypass time were extended for 56.9 minutes and 65.9 minutes, respectively, compared with the cases without a maze procedure. Four patients (brady atrial fibrillation 2, brady junctional rhythm 1, and complete AV block 1) required permanent pacemaker implantation. There was no operative death, but one patient who underwent the maze procedure and AVR + MAP + TAP died after 4 months due to pulmonary infection, sepsis and multiple organ dysfunction. This patient had shown low output syndrome for 3 days postoperatively. Having considered the data that the preoperative ejection fraction was 51%, cardiopulmonary bypass and cardiac arrest time were 200 min and 165 min respectively, occurrence of low cardiac output had been influenced by prolonged aortic cross-clamp. No late deaths have been observed in follow up period. In conclusion, maze procedure should not be performed in patients who have enlarged left atrium or complex cases requiring relatively longer operative time.
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PMID:[Evaluation of the results of the combined maze procedure for chronic atrial fibrillation with organic heart disease]. 1031 26