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Biomedical subjects

H Mitamura

Publications and source records attributed to H Mitamura.

At least 73 records · Page 4Linked to original sources
PubMed1995

Preinfarction angina as a major predictor of left ventricular function and long-term prognosis after a first Q wave myocardial infarction.

OBJECTIVES: The purpose of this study was to assess the prognostic significance of preinfarction angina after a first Q wave myocardial infarction. Patients with anterior or inferior myocardial infarction were compared. BACKGROUND: The effect of preinfarction angina on prognosis after anterior and inferior myocardial infarction remains unclear. METHODS: A total of 291 patients with a first Q wave anterior (n = 171) or inferior (n = 120) myocardial infarction were examined to assess the effect of preinfarction angina on short- and long-term prognosis. The relation between predischarge left ventriculographic findings and preinfarction angina was also examined. RESULTS: The presence of preinfarction angina was associated with lower peak creatine kinase activity, a lower in-hospital incidence of sustained ventricular tachycardia and fibrillation and a lower incidence of pump failure and cardiac mortality in patients with either anterior or inferior infarction. Among patients with anterior infarction, preinfarction angina was associated with a lower incidence of cardiac rupture and less need for readmission for heart failure within 1 year after the onset of infarction. In this subgroup it was also associated with a higher ejection fraction, a smaller end-diastolic volume and a lower incidence of aneurysm formation noted on ventriculography during convalescence. In patients with inferior infarction, these variables did not differ significantly in the presence or absence of preinfarction angina. Multivariate analysis confirmed that the presence of preinfarction angina was an independent predictor of development of ventricular aneurysm, late phase heart failure and 1-year cardiac mortality. CONCLUSIONS: The presence of preinfarction angina has a favorable effect on infarct expansion and late phase left ventricular function, especially in patients with anterior myocardial infarction. The mechanisms responsible for this phenomenon are not known but may be secondary to limitations of infarct size through unidentified mechanisms other than collateralization (e.g., ischemic preconditioning).

Adult↗
PubMed1995

ECG differentiation of idiopathic dilated cardiomyopathy from coronary artery disease with left ventricular dysfunction.

To elucidate electrocardiographic differences of dilated cardiomyopathy (DCM) and coronary artery disease (CAD) with left ventricular (LV) dysfunction, 12-lead electrocardiograms in 23 patients with DCM, 36 patients with CAD and LV dysfunction, and 63 normal subjects were analyzed. Abnormal Q waves were seen in 69% of CAD patients and in 26% of DCM patients. Abnormal Q waves in leads II, III, aVF, or V2-V4 were present in 61% of CAD patients compared with 4% of DCM patients (P < .001). The R wave in lead RV6 voltage in DCM was the highest among the three groups and correlated with the degree of LV dilatation. RV6 voltage in CAD was the lowest and decreased in proportion to the severity of the apical thallium-201 defect RV6 voltage of 15 mm or more was present in 78% of DCM patients compared with 11% of CAD patients (P < .001). The R waves in leads I, II, and III (RI, RII, RIII) were also low in DCM. Therefore, all voltage ratios of RV6/RI, RII, RIII were the highest in DCM. In particular, the ratio of RV6 over the maximum R wave in leads I, II, and III (RV6/Rmax) in DCM correlated with the degree of LV dilatation and inversely with ejection fraction. RV6/Rmax was significantly higher in the DCM group compared with the CAD and control groups (3.3 vs 1.2, 1.2, respectively; P < .001). This ratio of 3 or more was present in 61% of the DCM patients but in none of the CAD patients or normal subjects (P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiomyopathy, Dilated↗
PubMed1995

Nicorandil augments regional ischemia-induced monophasic action potential shortening and potassium accumulation without serious proarrhythmia.

Nicorandil is a clinically used nitrovasodilator that has a property as an opener of ATP-sensitive potassium (KATP) channels in vitro. We examined whether nicorandil at a clinically used dose augmented regional ischemia-induced monophasic action potential (MAP) shortening and increase in extracellular potassium concentration ([K+]o), and how it affected arrhythmia occurrence. Five-minute occlusion of a distal site of the left anterior descending coronary artery (LAD) was repeated at 30-min intervals in anesthetized open-chest dogs while recording MAP or measuring [K+]o with a potassium-sensitive valinomycin electrode from the epicardial center of the ischemic myocardium. Nicorandil (0.2-0.5 mg/kg) was administered intravenously (i.v.) 5 min before the third occlusion, and the data were compared with those during the second occlusion (control). During the second occlusion, MAP duration at 90% repolarization (APD90) shortened (mean rate for 5 min, 13 +/- 3%, n = 11) and [K+]o increased from 3.7 +/- 0.1 to 6.2 +/- 0.8 mM at 5 min (n = 12). These changes were reversed < or = 3 min after reperfusion. Before the third occlusion, baseline APD90 and [K+]o were not altered by nicorandil; however, the extent of occlusion-induced shortening of APD90 (25 +/- 4%) and [K+]o increase (7.8 +/- 1.6 mM) was augmented by the pretreatment. The drug effect was attenuated by a concomitant pretreatment with 5-hydroxydecanoate, a specific blocker of KATP channels (n = 2). The prevalence of ventricular fibrillation (VF) during occlusion/reperfusion sequence was reduced after nicorandil (1 of 25 vs. 5 of 25) without de novo VF. These results suggest that nicorandil at a clinical dose facilitates regional ischemia-induced activation of myocardial KATP channels without causing serious proarrhythmia. Such a property might help protect the myocardium against ischemia/reperfusion damage.

Action Potentials↗
PubMed1995

Beta-1-selectivity is not essential to achieve therapeutic efficacy with beta-blockade therapy for idiopathic dilated cardiomyopathy.

This study investigated the therapeutic efficacy of two different beta-blockers, metoprolol (beta 1-selective) and nipradilol (nonselective) for the treatment of idiopathic dilated cardiomyopathy (DCM). The New York Heart Association functional class improved in the metoprolol group (n = 9) and the nipradilol group (n = 9), but not in the control group who received conventional therapy (n = 8). The left ventricular ejection fraction increased in both the beta-blocker groups (p < 0.01, p < 0.05). Lymphocyte beta-adrenoceptors were upregulated in the nipradilol group (p < 0.01). Cardiac events were less common in both the beta-blocker groups than in the control group (both p < 0.05). Thus, nipradilol improved symptoms and cardiac function with a favorable effect on sympathoneuronal activity as well as metoprolol in patients with DCM. Therefore, beta 1-selectivity is not essential to achieve therapeutic efficacy with beta-blockade therapy for DCM.

Adrenergic beta-Antagonists↗
PubMed1994

Effect on short-term prognosis and left ventricular function of angina pectoris prior to first Q-wave anterior wall acute myocardial infarction.

The prognostic significance of angina pectoris before the development of first Q-wave anterior wall acute myocardial infarction (AMI) was assessed in 153 patients. A total of 100 patients in this study had angina before Q-wave AMI, whereas 53 patients had no antecedent symptoms of angina. The presence of angina before AMI was associated with a lower incidence of complications including sustained ventricular tachycardia or fibrillation (7% vs 25%, p = 0.0022), pump failure (24% vs 47%, p = 0.0035), cardiac rupture (1% vs 17%, p = 0.0001), and a lower in-hospital mortality rate (11% vs 28%, p = 0.0067). The peak creatine phosphokinase activity was lower in patients with than without antecedent angina (1,727 +/- 1,238 vs 2,675 +/- 2,569 IU/liter, respectively, p = 0.023). There was no difference in the prevalence of multivessel coronary artery disease or the presence of collateral circulation between the 2 groups. Left ventriculography revealed a higher left ventricular ejection fraction (54 +/- 13% vs 46 +/- 11%, p = 0.034) and smaller left ventricular end-diastolic volumes (75 +/- 15 vs 86 +/- 18 ml/m2, p = 0.017) in patients with than without antecedent angina. These findings suggest that the presence of angina before AMI may be associated with a protective effect on left ventricular function during anterior wall AMI. Although the precise mechanisms underlying the beneficial effects are unknown, they may be related to the development of collateral channels or ischemic preconditioning.

Adult↗
PubMed1994

Blockade of ATP-sensitive potassium channels by 5-hydroxydecanoate suppresses monophasic action potential shortening during regional myocardial ischemia.

We tested 5-hydroxydecanoate (5-HD), a specific blocker of ATP-sensitive potassium channels (IK.ATP), to determine if mitigates electrophysiologic changes produced by regional myocardial ischemia in vivo. A sequence of 5-minute occlusion of the distal LAD and 30-minute reperfusion was repeated while recording the monophasic action potential (MAP) and bipolar electrogram (EG) from the epicardial center of the ischemic myocardium in anesthetized dogs. 5-HD (30 mg/kg, i.v.) or glibenclamide (0.15 or 0.3 mg/kg, i.v.) was administered before the third occlusion, and the data were compared to the second occlusion data. 5-HD did not affect baseline MAP duration at 90% and 50% repolarization (APD90, APD50) before LAD occlusion but suppressed occlusion-induced shortening of APD90 (16 +/- 2% during the second occlusion vs. 5 +/- 3% during the third occlusion, n = 8, p < 0.01) and APD50 (16 +/- 3% vs. 10 +/- 3%, n = 8, p < 0.05). Pretreatment with glibenclamide also suppressed occlusion-induced MAP shortening and eliminated an additional effect of 5-HD (n = 3). 5-HD did not affect the occlusion-induced increase in duration and activation time of EG. 5-HD, as well as glibenclamide, suppressed regional ischemia-induced MAP shortening, probably by blocking activation of IK.ATP, without affecting conduction delay. These differential effects of 5-HD on repolarization and conduction during the early phase of regional ischemia might have the potential to suppress reentrant ventricular arrhythmias.

Action Potentials↗
PubMed1994

ECG characteristics of dilated cardiomyopathy.

To elucidate the electrocardiographic (ECG) characteristics of dilated cardiomyopathy (DCM), the authors analyzed the 12-lead ECGs and echocardiograms in 45 patients with DCM, 54 patients with left ventricular (LV) dilatation secondary to valvular heart disease (VHD), 101 hypertensive patients with LV hypertrophy, and 63 normal control subjects. In addition, serial ECG and echocardiographic changes in DCM during a mean follow-up period of 1.6 years were evaluated. Sokolow's criterion (S wave in lead V1 [SV1] + R wave in lead V5 or V6 [RV5 or RV6] > 35 mm) was met comparably in patients with DCM (69%), VHD (61%), and hypertension (74%) (P = NS). Notably, RV6 in DCM was the highest among the four groups and correlated with the degree of LV dilatation. In contrast, the R waves in leads I, II, and III (RI, RII, RIII) in DCM were the lowest and were not affected by the degree of LV dilatation, although RII and RIII in VHD and RI in hypertension correlated with the degree of LV dilatation and hypertrophy, respectively. As a result, all voltage ratios of RV6/RI, RII, RIII in DCM were not only the highest, but also increased linearly as the LV dilated progressively during the follow-up period. In particular, RV6 over the maximum R wave in leads I, II, and III (RV6/Rmax) in DCM correlated with the degree of LV dilatation and inversely correlated with ejection fraction. Subjects with DCM had a significantly higher RV6/Rmax than did patients with VHD, hypertension, and normal subjects (3.4 vs 1.7, 1.4, 1.2, respectively; P < .001), and this ratio of > or = 3 was seen in 67% of the DCM patients versus 4% of the VHD patients, 1% of the hypertensive patients, and 0% of the normal subjects. Thus, DCM commonly shows the ECG signs of LV hypertrophy, but characteristically has the high voltage ratios of RV6/RI, RII, RIII.

Cardiomyopathy, Dilated↗
PubMed1994

[Exercise and rest myocardial scintigraphy with 201TlCl/99mTc-MIBI dual energy acquisition using triple-energy window scatter correction].

We carried out dual 201Tl/99mTc-MIBI imaging, to reduce the time required for exercise myocardial scintigraphy. We investigated 4 different protocols. In protocol (A), Tl was injected at rest followed by the injection of MIBI at peak exercise. Dual SPECT images were obtained by 201Tl/99mTc simultaneous acquisition. Protocol (B) means reverse either, in which MIBI was injected at rest followed by the administration of Tl at peak exercise. In protocol (C), exercise was performed first with MIBI-injection, and then Tl was injected at rest after one hour later. Simultaneous acquisition was also performed. In protocol (D), after the rest Tl-imaging, MIBI was injected at peak exercise, and then the MIBI-imaging was done. In protocol (A), (B) and (C), simultaneous acquisition was performed using TEW (Triple-Energy Window) scatter correction. Thanks to using dual isotopes, all procedures could be completed within 1-2 hours, which was much shorter than the conventional myocardial perfusion imaging. Scatter correction was useful for accurate diagnoses, when the simultaneous imaging is performed.

Exercise Test↗
PubMed1993

[Clinical evaluation of myocardial perfusion imaging with 99mTc-tetrofosmin].

Myocardial perfusion imaging with Tc-99 m-1,2-bis (bis (2-ethoxyethyl) phosphino) ethane (Tc-99 m-tetrofosmin) was performed in 26 patients with ischemic heart disease (IHD) or suspected to have IHD. The agent was administered both at rest and at peak exercise. Exercise and rest studies were performed on the same day or on different days. The injected dose ranged from 296 MBq-740 MBq. Image quality was adequate for diagnosis, and was superior to that of T1-201 scintigraphy. Results from the tetrofosmin imaging corresponded well with findings of T1 scintigraphy, with a segmental concordance of 87%. Sensitivity and specificity were 70% and 93%, respectively. Our results suggested that tetrofosmin could be a promising Tc-99m labeling agent for the evaluation of myocardial perfusion.

Evaluation Studies as Topic↗
PubMed1993

Effect of E-4031, a new class III antiarrhythmic drug, on reentrant ventricular arrhythmias: comparison with conventional class I drugs.

We evaluated the antiarrhythmic efficacy of E-4031, a new class III drug, and compared it with that of conventional class I and II antiarrhythmic agents in terms of electrophysiological actions on refractoriness and conduction in a 7-day-old canine model of myocardial infarction. Sustained monomorphic VT was reproducibly induced in 26 dogs by a premature stimulation method from the right ventricle. Class I drugs (disopyramide, aprindine, flecainide) prevented VT induction in 5 of 13 dogs, and propranolol and E-4031 prevented it in 6 of 6 and 6 of 7 dogs, respectively. The effective refractory period (ERP) was determined at 47 epicardial sites overlying the infarct in each experiment by a S1S2 method. The standard deviation (SD) of the mean ERP of these sites was used as an index of ERP dispersion. The extent of ERP prolongation produced by class I drugs and E-4031 was significantly more marked than that produced by propranolol. However, the SD was increased by class I drugs and E-4031, but not by propranolol. Class I drugs increased the ERP dispersion mainly by an effect on the transmural infarct zone in which the control ERP was more prolonged than in the normal zone. E-4031 tended to prolong the ERP in both the normal and infarct zones, and had a minimal tendency to increase ERP dispersion. In contrast, propranolol decreased the ERP dispersion between zones. Conduction velocity calculated by epicardial mapping was significantly decreased by flecainide, but not by E-4031. We conclude that the antiarrhythmic effect of E-4031 depends largely on its ability to prolong refractoriness without suppressing conduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Acute myocardial infarction without warning: clinical characteristics and significance of preinfarction angina.

We investigated the clinical characteristics of acute myocardial infarction (AMI) not preceded by angina in 256 patients with first AMIs. Complications, including sustained ventricular tachycardia or ventricular fibrillation, pump failure and cardiac rupture, were more frequent in patients with AMI not preceded by angina (group 1, n = 92) than those preceded by angina (group 2, n = 164). The in-hospital mortality rate was higher in group 1 than in group 2. Poor preexisting collateral channels or lack of ischemic preconditioning may be responsible for the poorer outcome in group 1 patients.

Aged↗
PubMed1993

[Rest and stress myocardial perfusion imaging on the same day with two injections of 99mTc-tetrofosmin].

99mTc-tetrofosmin myocardial perfusion imagings under different protocols were performed at rest and stress on the same day. In the stress/rest protocol, the exercise study was carried out first, and then the rest one followed. Eight patients were involved in the stress/rest protocol. Seven patients were examined in the reverse, rest/stress protocol. In any protocols, the injection interval was 3 hours, and injection doses in the first and second studies were 370 MBq and 740 MBq, respectively. Myocardial counts were obtained by placing region of interest over the myocardial walls in short axial SPECT images. Based on myocardial counts from the first injection and the wash-out rate of tetrofosmin, we calculated, at the second imaging, counts caused from the first injection. Approximately 20-25% of counts in the second study were found to be caused from the residual radiotracer. The residual radiotracers affected the interpretation of imagings of two patients we examined: one with marked reversible ischemia examined in the stress/rest protocol and the other with mild ischemic change examined in the rest/stress one. Our results suggested that some modifications of studies, such as the increase in the injection intervals or the reduce of the first-to-second dose ratio, might be necessary to conduct the same day protocols.

Exercise Test↗
PubMed1992

[Characteristics of acute myocardial infarction, preinfarct angina and postinfarct angina in patients with diabetes mellitus].

To elucidate the characteristics of acute myocardial infarction, preinfarct angina and postinfarct angina in diabetic patients, we compared 51 diabetics and 73 non-diabetics who had myocardial infarction and angiographically-proven coronary artery stenosis. There was no statistical difference between these 2 groups with respect to age, sex, histories of smoking, hypertension and hypercholesterolemia, and hemodynamic parameters. Mean of the number of diseased vessels and of the jeopardy scores were higher in diabetics than in non-diabetics (2.4 vs. 1.9, p < 0.01; 7.2 vs. 5.7, p < 0.02, respectively). The absence of preinfarct angina (59 vs 32%, p < 0.01) and typical chest pain of myocardial infarction was more frequent in the diabetic group than in the non-diabetic group (43 vs 15%, p < 0.005). Congestive heart failure was more common in diabetics than in non-diabetics (45 vs 14%, p < 0.005). Though there was no difference in the frequency of postinfarct angina between the 2 groups (54 vs 52%), painless myocardial ischemia during treadmill exercise tests was more frequent in diabetics than in non-diabetics (75 vs 30%, p < 0.025). Compared to diabetic patients with typical chest pain of myocardial infarction, diabetics without typical chest pain had preinfarct angina less frequently (82 vs 41%, p < 0.01), but had diabetic neuropathy (71 vs 43%, p < 0.05) and retinopathy (67 vs 32%, p < 0.025) more frequently. We concluded that diabetic patients with myocardial infarction frequently lack 1) preinfarct angina, and 2) typical chest pain of myocardial infarction. 3) They often suffer from congestive heart failure, 4) frequently accompanied by painless myocardial ischemia during exercise stress tests. Therefore, special attention should be paid for the management of diabetic patients with specific neuropathy and retinopathy.

Aged↗
PubMed1990

[Painless myocardial ischemia in diabetic patients with coronary artery disease: evaluations by treadmill exercise tests].

To elucidate the prevalence and features of painless myocardial ischemia among diabetic patients, 44 consecutive patients with angiographically-documented coronary artery disease and positive treadmill tests were examined. They were 26 with diabetes and 18 without it. Painless myocardial ischemia was defined as the absence of chest pain with 1 mm or more ST segment depression during the exercise stress tests. The severity of ischemia was determined by the magnitude of the ST segment depression. Painless myocardial ischemia was observed in 18 of the 26 (69%) diabetics, and in three of the 18 (17%) non-diabetics (p less than 0.005). The frequency of painless ischemia in the diabetics was relatively high regardless of the severity of ischemia, while painless ischemia was less frequent in the non-diabetics with severe ischemia. With a level of 2.5 mm ST depression, 11 of 12 (92%) diabetics were free of pain compared to four of 11 (36%) non-diabetics (p less than 0.01). Absence of chest pain during the exercise tests was not concordant with prior angina in diabetics, as opposed to non-diabetics in whom both clinical and exercise-induced angina developed concordantly. The diabetic patients without chest pain had a higher prevalence of three major diabetic complications such as neuropathy, nephropathy and retinopathy compared to those developing chest pain (p less than 0.025). It was concluded that in diabetics, painless myocardial ischemia is frequently observed during exercise stress tests and its prevalence is relatively high regardless of the severity of ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1990

[Incidence of atrial septal aneurysm: echocardiographic and pathologic analysis].

We prospectively studied the echocardiographic findings of an atrial septal aneurysm (ASA) to estimate its incidence and to clarify its clinical characteristics and significance. Post-mortem examination was also performed in three patients. Echocardiographically, ASA was defined as a bulging segment of the atrial septum localized in the fossa ovalis, either fixed in one direction or oscillating between the atria. It was classified in three types according to Hanley et al., i.e., Type 1A, protruding into the right atrium without oscillation; Type 1B protruding into the right atrium with oscillation, and Type 2, protruding into the left atrium with oscillation. Among 2,074 consecutive subjects in the echocardiographic study population, ASA was diagnosed in 26 patients (1.2%). This figure was slightly higher than those previously reported (0.6% to 1.0%). The extent of protrusion of the aneurysm was 8 mm or more in all patients, regardless of its direction, and it was assumed that this is a reasonable echocardiographic diagnostic criterion in the apical four-chamber view. All patients were over 51 years in age, with a mean of 71 years. Most patients (96%) had oscillation of their aneurysms. Twenty-one patients (81%) were of Type 2; one was Type 1A, and four were Type 1B. Post-mortem examination of three patients revealed septal protrusion toward the right atrium in all, and patent foramina ovale in two of them. Among the 26 patients, two (8%) had systemic embolic complications; one, cerebellar infarction, the other, cerebral infarction and mesenteric artery embolism. In conclusion, atrial septal aneurysm was observed in 1.2% of subjects undergoing routine echocardiography, with a distinctive distribution among patients over 51 years of age. Characteristically, it protrudes into the left atrium 8 mm or more, and it is sometimes associated with patent foramen ovale. Systemic embolism is a possible complication of this anomaly.

Aged↗
PubMed1990

[Echocardiographic documentation of the instant of cardiac rupture: a case report].

The instant of cardiac rupture was initially recorded using two-dimensional echocardiography in a patient with acute myocardial infarction. This 70-year-old woman was admitted to our hospital because of chest pain lasting for six hours. The admission electrocardiogram showed Q waves and S-T segment elevations in leads I, aVL, and V4-6. Two-dimensional echocardiography revealed hypokinesis in the middle and apical portions of the anterior septum and hyperkinesis in the basal portion of the anterior septum and the posterior wall. When the patient suddenly lost consciousness, echocardiography detected a rapidly developing pericardial effusion, which filled the pericardial sac within 13 sec. A myocardial tear was recognized at the apex of the left ventricle between portions of the hypokinesis and hyperkinesis. A simultaneously-recorded electrocardiogram showed sinus rhythm (84/min) which did not change at the moment of rupture and lasted further for 15 sec until a sudden alteration to sinus bradycardia (46/min) occurred. Cardio-pulmonary resuscitation was unsuccessful and the patient died. This is the first such case in the medical literature in which the instant of cardiac rupture was recorded. Detailed reviews of the video tapes revealed that rapid accumulation of pericardial fluid occurred, followed by transient sinus bradycardia, most likely due to vagal reflex to the stretched pericardium.

Aged↗
PubMed1989

Extracellular potassium ion dynamics and ventricular arrhythmias in the canine heart.

The relation between extracellular potassium ion activity [( K+]o) and ventricular tachyarrhythmias was studied in an open chest canine model with the use of two protocols. In Protocol I, potassium chloride was administered into the proximal left anterior descending coronary artery at a rate of 0.125 mEq/min for either 20 min or until [K+]o = 20 mEq/liter, whichever came first. In Protocol II, the proximal left anterior descending coronary artery was occluded in one step and was reperfused 20 min later. Fifteen dogs were subjected to Protocol I, nine of which were also subjected to Protocol II. In the latter group, a recovery period of greater than or equal to 1 h separated the two protocols. Local K+ and intramyocardial activities were recorded with use of bifunctional ion-sensitive plunge electrodes at multiple sites located in the region of the left ventricle perfused by the left anterior descending artery and at one site outside of this region. The following variables were recorded and analyzed: Lead II electrocardiogram, heart rate, systemic arterial blood pressure, local [K+]o and its time derivative (dK+/dt), local electrograms and ventricular arrhythmias. Maximal [K+]o and dK+/dt were 23 +/- 3 mEq/liter and 9 +/- 1 mEq/liter per min in Protocol I and 14 +/- 1 mEq/liter and 3 +/- 1 mEq/liter per min in Protocol II, respectively. In both protocols, the occurrence of ventricular arrhythmias correlated with [K+]o (p less than 0.02) as well as with dK+/dt (p less than 0.05). Ventricular arrhythmias were more frequent and more severe in Protocol II than in Protocol I (p less than 0.05). Therefore, whereas K+ dynamics were more pronounced in Protocol I, ventricular arrhythmias were more severe in Protocol II. This occurrence was apparently due, at least in part, to less heterogeneous changes in K+ gradients during constant K+ infusion. It was concluded that, in addition to the magnitude of [K+]o, the rate of change of this variable (that is, dK+/dt) apparently plays an important role in the genesis of ischemic ventricular arrhythmias.

Animals↗