摘要:

To assess left ventnrcular (LV) diastolic filling at rest in patients with coronary artery disease (CAD), we analyzed high-resolution time-activity curves (10-20 msec/frame) obtained from gated radionuclide angiograms in 231 patients. Peak LV filling rate (PFR), expressed in end-diastolic volumes per second (EDV/sec), was subnormal in CAD patients (1.8 ± 0.6 [±SDJ vs normal mean of 3.3 ± 0.6, p < 0.001) and time to PFR (TPFR), measured from end-systole to PFR, was prolonged (171 i 41 msec vs normal mean of 136 ± 23 msec, p < 0.001). These indexes were also abnormal in the 141 patients with normal resting LV ejection fraction (PFR = 2.1 ± 0.5 EDV/sec; TPFR = 175 ± 36 msec) and in 123 patients without Q waves on the ECG (PFR = 2.1 ± 0.5 EDV/sec; TPFR = 168 ± 38 msec). Abnormal LV filling at rest (PFR < 2.5 EDV/sec or TPFR > 180 msec) was found in 91% of all patients with CAD, 86% of patients with normal resting LV ejection fractions, 85% of patients without Q waves, and 82% of patients with normal resting LV ejection fraction, no resting regional wall motion abnormalities and no Q waves. Thus, LV diastolic filling, evaluated noninvasively by radionuclide angiography, is abnormal in a high percentage of patients with CAD at rest independent of LV systolic function or previous myocardial infarction.Electrophysiologic studies using the His bundle electrogram (HBE) and histologic studies of serial sections of the conduction system were correlated in two groups of deceased patients. Group 1 consisted of five patients with chronic complete atrioventricular block (CAVB) who had narrow QRS complexes and AH block (block proximal to the His bundle deflection). Group 2 consisted of four patients with chronic CAVB who had wide QRS complexes and HV block (block distal to the His bundle deflection).In group 1, the sites of the main lesion were not located in the approaches to the atrioventricular (AV) node or the AV node, but were found in the penetrating portion of the His bundle in one patient and in the branching portion of the His bundle in three patients. In the remaining patient, the main site of block could not be demonstrated histologically in the AV conduction system, but marked fibrosis of the approaches to the sinoatrial node and surrounding atrial muscle was found. In all patients of group 2, the site of the main lesion was located in the bilateral bundle branches, and thus was compatible with so-called trifascicular block.This correlation study between the His bundle electrogram and histologic findings of the AV conduction system showed that in some cases, CAVB presenting as AH block on the HBE can be associated with a lesion in the branching portion of the His bundle (distal His), and that CAVB presenting as HV block on the HBE is associated with a bilateral lesion of the bundle branches.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Small, high-frequency electrocardiographic signals were recorded from the body surface in 39 patients with and 27 patients without ventricular tachycardia (VT). All patients were in normal sinus rhythm, had a previous myocardial infarction, were not taking antiarrhythmic drugs, and did not have bundle branch block. Bipolar X, Y, Z leads were signal averaged and processed by a bidirectional digital filter that allowed low-amplitude signals to be detected in the terminal QRS complex and ST segment. The high-pass filter frequency was 25 Hz.Patients with VT had a lower amplitude of high-frequency signal in the late QRS complex. In the last 40 msec of the filtered QRS complex, the patients with VT had 14.9 - 14.4 MV of high-frequency signal; patients without VT had 73.8 ± 47.7 gV (p < 0.0001). Ninety-two percent of the patients with VT had less than 25 pV of high-frequency voltage; only 7% of patients without VT had less than 25 MV (p < 0.0001). Patients with VT had a longer QRS duration than those without VT, 139 ± 26 vs 95 4- 10 msec (p < 0.0001). The QRS duration was longer than 120 msec in 72% of the patients with VT but in none of thepatients without VT (p < 0.0001). In all patients there was no separate and discrete high-frequency signal in the ST segment. Advanced signal processing of the ECG accurately identified the patients in the study with VT after myocardial infarction.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

We examined the feasibility of using a standby automatic implantable defibrillator and established thresholds for internal defibrillation. The implantable defibrillator senses ventricular fibrillation and delivers an electrical impulse for defibrillation. Two lead systems for the device have been investigated. System I consists of two 12-cm2silicone-covered titanium mesh patches attached to the atrial and diaphragmatic pericardial surfaces. System II has an identical diaphragmatic patch and a titanium spring catheter, with a 12-cm2surface area of conductivity, placed transvenously in the right atrium. Both systems were implanted by thoracotomy in 12 dogs (mean weight 20 kg) and by a subxiphoid approach in 10 pigs (mean weight 20 kg). The defibrillation threshold (lowest energy required for 80% success) was determined periodically for 54 weeks in the dogs (615 trials) and at 6 weeks for the pigs (100 trials).In dogs, the mean defibrillation threshold with system I leads at 4 weeks was 10.5 J and did not change significantly over a 54-week period (p > 0.05). Similar results were obtained in the pig at 4 weeks. The defibrillation thresholds for both lead systems in dogs and pigs using a transpleural thoracotomy or a subxiphoid approach are satisfactory for an implantable defibrillator that produces 20-35 J.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

In the steady state, the refractory periods of the human atrium, atrioventricular (AV) node, and ventricle are a function of cycle length. We compared the change in refractoriness that occurred when these refractory periods were measured after eight beats at a shorter cycle length with the change that occurred when these refractory periods were measured after a single beat at the shorter cycle length. For a decrease in cycle length of 235 ± 63 msec, the atrial effective refractory period shortened 31 ± 24 msec (p < 0.01) when measured after eight beats at the shorter cycle length and 26 ± 24 msec (p < 0.01) when measured after a single beat at the shorter cycle length. Similar changes were seen in atrial functional refractory period. For a decrease in cycle length of 214 ± 63 msec, the AV nodal effective refractory period increased 30 ± 39 msec (p < 0.05) when measured after eight beats and 31 ± 34 msec (p < 0.05) when measured after a single beat. The AV nodal functional refractory period showed moderate shortening with decreases in cycle length, both when measured after eight beats and when measured after a single beat (p = NS). For both the atrium and AV node, there was no significant difference between the change in refractoriness after a single beat at the shorter cycle length and after eight beats at the shorter cycle length. For a decrease in cycle length of 175 ± 52 msec, the ventricular effective refractory period shortened 26 ± 10 msec (p < 0.01) when measured after eight beats and 16 ± 12 msec (p < 0.01) when measured after a single beat at the shorter cycle length. Thus, a single beat at the shorter interval produced 60% of the shortening of refractoriness produced by eight beats at the shorter interval (p < 0.01). These findings have implications for the performance and interpretation of stimulation studies and provide insight into the mechanism of initiation of tachycardia by premature beats.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

A multivariate decision-theoretic electrocardiogram (ECG) classification scheme called Cardiac Infarction Injury Score (CIIS) was developed using ECGs of 387 patients with myocardial infarction (MI) and 320 subjects without infarction. The most accurate and stable classification was achieved by using a combination of eight binary (single threshold), three ternary (two thresholds), and four ECG features measured on a continuous scale. For practical visual coding of ECGs, the CIIS coding procedure uses a checklist containing 12 items measured from the conventional 12-lead ECG.The CIIS test results indicate that, in comparison with conventional ECG criteria for MI used in clinical trials, the diagnostic accuracy can be considerably improved by optimizing feature and threshold selection and by multivariate analysis. The CIIS detected MI with a sensitivity of 85% and a specificity of 95%. Using a higher severity level, a specificity of 99% was achieved, with a sensitivity of 71%. One of the primary uses of the CIIS is coding of significant worsening of the ECG with new coronary events from annually recorded ECGs in clinical trials and epidemiologic studies.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

The QRS morphology of the 12-lead ECG of 41 morphologically distinct ventricular tachycardias (VT) was correlated with their site of origin as determined by catheter and intraoperative mapping. Twenty-two VT patterns had a right bundle branch block (VT-RBBB) morphology and 19 a left bundle branch block (VT-LBBB) morphology. All VT-RBBBs arose in the left ventricle. All 16 VT-LBBBs in patients with coronary artery disease (CAD) arose from the LV at sites on or adjacent to the septum. Three VT-LBBBs in patients without CAD arose in the right ventricle. The 12-lead ECG could not precisely identify the site of origin in patients with CAD but could differentiate anterior from posterobasal regions, particularly in VTLBBB. The ECG was less useful in localizing VT-RBBB because of overlapping patterns. General patterns that were useful in differentiating anterior from posterobasal sites of origin included: (1) The presence of a q wave in leads 1 and V, was seen in VT-RBBB or VT-LBBB originating anteriorly but not in VT of posterobasal or posterior septal origin. (2) R waves in leads 1 and V, to V, in VT-RBBB, and in leads 1, V2, V3 and V6 in VT-LBBB were specific for a posterior origin, and not observed in VT of anterior origin. (3) In VT-LBBB with a superior axis, a q wave in leads 1 and V6 was specific for origin along the inferior aspect of the anterior septum. (4) All VT-LBBB with an inferior and rightward axis originated from the superior aspect of the anterior septum. We conclude that although selected ECG features are useful in locating the origins of VT, precise localization is not possible by the ECG alone.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Twenty-three patients with sustained, recurrent, symptomatic ventricular tachycardia were treated with oral amiodarone. Initial doses were 600-2000 mg/day and maintenance doses were 200-1200 mg/day. Amiodarone was highly effective in 20 patients (87%), seven of whom had a follow-up of 30 months or longer, including two who were followed for 5 years. Three patients died within the first 45 days, three died suddenly after a follow-up of 33.5 months, and four had a nonarrhythmic death after a follow-up of 25 months. Fifteen patients (65%) had no recurrence during a follow-up of 21.5 months, while five (22%) had isolated recurrences during a follow-up of 32.2 months. The average maintenance dose was 713 mg/day in the 15 patients who did not have recurrences and 375 mg/day in the five patients who had recurrences (p < 0.001). Both short- and long-term tolerance were excellent and there was not a single case in which treatment had to be discontinued. The main disadvantage of amiodarone was that it took an average of 9.5 days to reach antiarrhythmic efficacy. The main advantages were prolonged duration of action (recurrences occurred only 15-60 days after the drug was discontinued or the dose lowered, virtual absence of contraindications, doses as high as 2000 mg/day were safe and patient compliance was excellent.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

We compared the relationship between plasma levels of procainamide and suppression or prevention of various forms of ventricular arrhythmias in 18 patients, six of whom had premature ventricular complexes (PVCs) during acute myocardial infarction (AMI), six of whom had PVCs in the setting of stable chronic ischemic heart disease (CIHD), and six of whom had recurrent symptomatic ventricular tachycardia (VT) with chronic PVCs between episodes of VT. The mean plasma level of procainamide required for 85% suppression of PVCs in the AMI patients was 5.0 ± 0.5, g/ml, while that required for the CIHD patients was 9.3 ± 0.7 gg/ml (p < 0.05). The mean plasma level required for prevention of spontaneous episodes of symptomatic sustained tachycardia in the VT group was 9.1 ± 3.4, g/ml, while the mean level required for 85% suppression of PVCs in the same patients was 14.9 ± 3.8, g/ml (p < 0.01). In the VT group, PVC frequency was decreased by a nmean of only 36% (range 11-63%) at plasma levels of procainamide sufficient to prevent spontaneous VT. The relationship between plasma levels of procainamide and PVC suppression appears to be different in AMI and CIHD patients; furthermore, a high degree of PVC suppression is not a necessary endpoint of antiarrhythmic therapy when attempting to protect patients against recurrent symptomatic VT.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

We determined the pharmacokinetics, efficacy and therapeutic plasma concentration of encainide, a new antiarrhythmic drug that affects His-Purkinje conduction but not ventricular refractoriness. Nine patients with frequent and complex premature ventricular complexes were studied in a 3-day double-blind protocol. Each day, each patient received 75 mg of i.v. or oral encainide or placebo. Frequent blood samples for encainide plasma concentration determination and continuous ambulatory ECGs were obtained. There was a marked intersubject variation in bloavailability (mean 42 ± 24%, range 7.4-82%), clearance (13.2 ± 5.6 mI/min/kg, range 3.75-22.1 ml/min/kg) and half-life (3.4 ± 1.7 hours i.v., 2.5 ± 0.8 hours oral). Eight of nine patients had more than 90% suppression of premature ventricular complexes for 3-36 hours. Minimal antiarrhythmic plasma concentration was higher (39 ± 54 ng/ml, range 3.5-170 ng/ml) after i.v. dosing than after oral dosing (14 ± 16 ng/ml, range 1.5-48 ng/ml), suggesting an active metabolite after oral dosing in many patients. Minimal side effects were seen despite high peak plasma concentrations (range 794-1556 ng/ml i.v., 36-495 ng/ml oral). The minimal ratio of toxic to therapeutic plasma concentration ranged from 4.3-326 (median 23) after oral dosing. Antiarrhythmic action was associated with an 11-44% widening of the QRS complex that was not associated with other adverse effects. We conclude that encainide effectively suppresses ventricular arrhythmias. Despite a variable bioavailability, high clearance and short half-life, its wide ratio of toxic to therapeutic concentration and probable active metabolite permit a long duration of action, which should allow a reasonable dose schedule in most patients during chronic oral dosing.

ISSN:0009-7322    

出版商:OVID    

年代:1981

数据来源: OVID