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Biomedical subjects

P Denes

Publications and source records attributed to P Denes.

At least 73 records · Page 4Linked to original sources
PubMed1983

Significance of ventricular tachycardia in idiopathic dilated cardiomyopathy: observations in 35 patients.

To evaluate the significance of ventricular tachycardia (VT) in idiopathic dilated cardiomyopathy (IDC), 35 consecutive patients seen between 1976 and 1980 were studied. The criteria for diagnosis of IDC were based on clinical, laboratory, and cardiac catheterization findings. All patients had right and left heart catheterization, left ventriculography, and coronary cineangiography. Long-term ambulatory electrocardiograms (Holter) were obtained in all patients at the time of diagnosis. There were 24 male and 11 female patients aged 22 to 72 years (mean +/- standard deviation [SD]51 +/- 12). Frequent ventricular premature beats (VPB) (30/h) were observed in 29 patients (83%): complex VPB (Lown grades 3, 4, and 5) in 93% and simple VPB in 7%. Twenty-one patients (60%) had nonsustained VT consisting of 3 to 46 beats (8 +/- 5) with rates from 75 to 210/min. No difference between patients with and those without VT was observed in regard to the presenting symptoms, functional classification, electrocardiographic findings, heart size on chest X-ray, and the hemodynamic measurements including cardiac index, left ventricular end-diastolic pressure, and ejection fraction. Patients with VT were older (p less than 0.05). Follow-up observation from 4 to 74 months (34 +/- 17) showed that 2 patients died suddenly (1 with and 1 without previous VT), a third patient died from intractable congestive heart failure, and the fourth from sepsis. It is concluded that (1) the incidence of ventricular arrhythmias in IDC is high, (2) VT is frequent and tends to occur in the nonsustained form, and (3) there is no correlation between VT and the clinical and hemodynamic findings. VT does not appear to predict prognosis during a relatively short follow-up period in patients with IDC.

Adult↗
PubMed1983

Clinical electrophysiology--a decade of progress.

During the past 14 years there have been major advances in the field of clinical electrophysiology. This progress is a result of a more extensive use of intracardiac electrode catheters with recordings from multiple sites in the right and left cardiac chambers, the introduction of programmed electrical stimulation techniques and the use of antiarrhythmic drugs for diagnostic and therapeutic purposes during acute electrophysiologic testing. This article examines the pioneering studies and the subsequent developments in the field of clinical electrophysiology. The specific topics that are reviewed include the sinus node and atrium, atrioventricular conduction, supraventricular tachycardia and ventricular tachycardia. The therapeutic implications of each topic are also discussed. Clinical electrophysiology in its initial stages was a descriptive technique, but has since become an important diagnostic and therapeutic tool. However, electrophysiologic testing is an intensive process, requiring specialized training and a substantial commitment of human and physical resources.

Arrhythmias, Cardiac↗
PubMed1983

Normal electrophysiological findings in a patient with symptomatic intermittent advanced atrioventricular block.

This report describes an otherwise healthy young woman who presented with syncope during episodes of advanced atrioventricular (AV) block. The His bundle recordings during normal sinus rhythm and atrial and ventricular pacing were normal. Carotid sinus massage produced no abnormality. Subsequently, the patient received a permanent pacemaker and has been free of symptoms. Intermittent advanced AV block has been observed on follow-up electrocardiograms. This unique case demonstrates a potential limitation of routine electrophysiologic investigation.

Adult↗
PubMed1983

Dual AV nodal pathways--vagal influences on AV nodal conduction.

This 52-year-old male presented with syncope and demonstrated two distinct PR intervals on the electrocardiogram. Electrophysiologic studies showed dual AV nodal pathways. Right-sided carotid sinus massage induced prolonged periods of sinus arrest with no change in AH interval. Left-sided carotid sinus massage produced long AH intervals (slow pathway conduction) with some slowing of sinus rate. Whenever sinus rhythm with slow pathway conduction was observed (long AH) a 20-30 mmHg drop systolic pressure was seen. Following implantation of an AV sequential pacemaker, the patient has been asymptomatic.

Arrhythmias, Cardiac↗
PubMed1983

Quantitative analysis of the high-frequency components of the terminal portion of the body surface QRS in normal subjects and in patients with ventricular tachycardia.

Quantitative analysis of the high-frequency components of the terminal portion of the surface QRS was performed in 42 normal subjects (group 1, ages 18-67 years, mean +/- SEM 34.7 +/- 2.2 years) and in 12 patients with symptomatic, sustained ventricular tachycardia (VT) (group 2, ages 48-76 years, mean 59 +/- 2.3 years). Signal averaging and high-pass, bidirectional digital filtering were used for analysis. The total duration of the QRS, the duration of the low-amplitude signals (less than 40 microV) in the terminal portion of the QRS and the amplitude of the signals in the last 40 and 50 msec of the QRS were measured at filter settings of 25 and 40 Hz. Reproducibility of the measurements was tested in 15 normal subjects by comparing results obtained from two consecutive recordings. Significant differences were found between normal subjects and VT patients for all four indexes at both 25- and 40-Hz filters. Specific values for each of the indexes were identified at the 40-Hz filtering, which could separate normal subjects from VT patients (20 microV for the amplitude of last 40 msec; 30 microV for the amplitude of last 50 msec; 120 msec for the total duration; and 39 msec for the low-amplitude signal of the filtered QRS). Using these values for the four indexes, respectively, 90%, 98%, 100% and 90% of the normal subjects and 83%, 83%, 58% and 83% for the VT group were correctly classified. The results show that the high-frequency analysis of the signal-averaged body surface QRS is a reliable, reproducible, noninvasive method for distinguishing patients with VT from normal subjects.

Adolescent↗
PubMed1982

The effect of left ventricular aneurysmectomy on the electrocardiogram: a study of 77 patients and review of the literature.

UNLABELLED: Electrocardiograms (ECGs) were reviewed in patients undergoing left ventricular aneurysmectomy. Post-operatively, significant decreases were noted in ST segment elevation (p less than 0.001) and anterior (p less than 0.03) and inferior R wave heights (p less than 0.002). In addition, abnormal Q waves disappeared in 50% of patients. Comparison of ECG changes between survivors and patients dying of cardiac related events revealed that patients with a preoperative axis of greater than or equal to 60 degrees, postoperative leftward axis shifts and a marked decrease in ST segment elevation and/or R wave height had significantly higher mortality. CONCLUSION: 1) Left ventricular aneurysmectomy affects ventricular depolarization as evidenced by a significant loss of R wave height and changes in infarct pattern; 2) LVA affects ventricular repolarization as evidenced by a significant decrease in ST elevation; 3) the ventricular aneurysm appears to contain "viable muscle" that contributes to ventricular depolarization and remains partially depolarized during diastole; and 4) there are prognostic electrocardiographic parameters, which correlate with mortality during postoperative follow-up.

Adult↗
PubMed1982

Unipolar sensing abnormalities: incidence and clinical significance of skeletal muscle interference and undersensing in 228 patients.

Compared to bipolar lead configurations, unipolar pacing systems presumably enhance sensing of cardiac electrical events but are ore susceptible to electrical interference, including skeletal myopotentials. The incidence and clinical significance of oversensing and of undersensing by unipolar R-wave inhibited pacemakers in 228 patients were assessed by 24-hour Holter monitoring and/or by pectoral muscle exercises. Overall, 38% of patients exhibited oversensing and false inhibition due to skeletal myopotentials. Symptoms due to oversensing occurred in 14% of patients and 58% of these required corrective intervention. The presence of silastic coating on the pulse generator had no effect on the sensing of myopotentials. In addition, the incidence of undersensing as assessed by Holter monitoring was 17% despite adequate implantation R wave amplitudes. Thus, oversensing remains a major clinical problem when using unipolar pacemaker systems and their use has not eliminated undersensing.

Electrophysiology↗
PubMed1982

Incessant junctional reciprocating tachycardia caused by dual atrioventricular nodal pathways and atrio-nodal bypass tract.

A case is described with clinical and electrocardiographic findings of incessant junctional reciprocating tachycardia. Electrophysiological study showed that longitudinal dissociation of the atrioventricular node into two pathways was responsible for the maintenance of the arrhythmia. The two intranodal pathways had different refractory periods but reciprocally related and overlapping conduction times (anterograde fast, retrograde slow, and vice versa). Induction and termination of the arrhythmia was related to the presence of a partial atrio-nodal bypass tract.

Atrioventricular Node↗
PubMed1982

Noninvasive identification of initial site of abnormal ventricular activation by least-square phase analysis of radionuclide cineangiograms.

Least-square phase analysis (LSPA) of radionuclide cineangiograms demonstrates the sequence of onset of inward ventricular movement noninvasively. To validate the method and explore its ability to identify abnormal initial sites of ventricular activation, LSPA was applied to 14 patients with pacemakers (one with electrodes in two locations) (group 1) and three patients with recurrent ventricular tachycardia (VT) (group 2) who had undergone electrophysiologic endocardial mapping. The segment in which the site of initial ventricular activation was located was correctly identified in 13 of 15 paced studies and in two of three group 2 patients during VT. Pacing increased the duration of spread of onset of inward ventricular movement, and the duration of spread of onset correlated well with the duration of the QRS (r = 0.80). The sequence of onset of inward ventricular movement during VT was similar to the sequence of depolarization in all three group 2 patients. These preliminary results suggest that the sequence of onset of ventricular contraction as depicted by LSPA is a valid representation of the actual contraction sequence and that LSPA or radionuclide cineangiography correctly identifies abnormal sites of initial ventricular activation.

Arrhythmias, Cardiac↗
PubMed1982

Sequence and timing of ventricular wall motion in patients with bundle branch block. Assessment by radionuclide cineangiography.

We determined the sequence and timing of inward ventricular wall motion by least-square phase analysis of radionuclide cineangiograms in 10 patients with left bundle branch block (LBBB), five patients with right bundle branch block (RBBB) and 11 patients with normal conduction. All LBBB and RBBB patients had normal coronary arteries and no segmental wall motion abnormalities. The left ventricle (LV) was divided into eight segments and the right ventricle (RV) into three; sequence and timing were scored by three observers. In normal subjects, wall motion begins in either or both ventricles and ends in the LV or both ventricles. In patients with LBBB it begins in the RV and ends in the LV; in patients with RBBB is begins in the LV and ends in the RV or both ventricles. The intraventricular wall motion is also altered in the ventricle ipsilateral to a bundle branch block. In LBBB, the mean time of onset of LV wall motion is delayed 1.9 frames (38 msec), whereas RV wall motion is normal. In RBBB, the onset of RV wall motion is delayed 1.3 frames (26 msec), whereas LV wall motion is not delayed.

Adult↗
PubMed1982

The effect of intermittent bundle branch block on the coupling interval of ventricular premature depolarizations.

The mechanism of origin of ventricular premature depolarizations (VPDs) is explained by automaticity or reentry. We studied three patients with intermittent left bundle branch block (LBBB) and unifocal VPDs of right bundle branch block (RBBB) morphology (assumed left ventricular origin). We examined the effect of different types of intraventricular conduction on the coupling intervals of the VPDs. Specifically, we proposed that the coupling intervals of VPDs would be longer during LBBB conduction of sinus beats (ipsilateral to the ventricle of origin of VPDs) compared with the coupling intervals during normal intraventricular conduction. We found that the coupling intervals during LBBB were significantly longer than those during normal conduction in all three cases (patient 1, 596 +/- 7 vs 484 +/- 5 msec; patient 2, 639 +/- 9 vs 534 +/- 11 msec; patient 3, 444 +/- 4 vs 382 +/- 9 msec) (p less than 0.005). We also examined the length of the preceding RR intervals and counted sinus beats intervening between successive VPDs (S values). One case demonstrated S values suggestive of concealed bigeminy; the other cases had S values suggesting concealed bigeminy and its variants. We have demonstrated that some VPDs are dependent on an initiating sinus beat. This dependence on a preceding beat is consistent with both a reentrant mechanism or triggered automaticity.

Bundle-Branch Block↗
PubMed1981

Clinical, electrocardiographic and follow-up observations in patients having ventricular fibrillation during Holter monitoring. Role of quinidine therapy.

Ventricular fibrillation occurred during Holter electrocardiographic monitoring in 5 of 3,307 consecutive patients. All five patients had Holter studies for evaluation of antiarrhythmic drug therapy; their ages ranged from 51 to 65 years. No patient had acute myocardial infarction; all had congestive heart failure and severe left ventricular dysfunction. One patient had ischemic and four had nonischemic cardiomyopathy. All patients had recently begun treatment with oral quinidine and had plasma quinidine levels of 1.24 to 5.18 microgram/ml. The Holter monitoring revealed that all had a long Q-T interval and that ventricular fibrillation began during frequent ventricular premature beats and was immediately preceded by ventricular tachycardia of the torsade de pointes type. The coupling interval of the ventricular premature beats initiating torsade de pointes was late (440 to 720 ms) and followed long preceding cycles (840 to 1920 ms). Ventricular fibrillation resolved spontaneously in two patients, but two of the remaining three patients died despite attempted cardiopulmonary resuscitation. It is concluded that (1) left ventricular dysfunction, chronic ventricular arrhythmias and initiation of quinidine therapy were the common findings in these patients; (2) a long Q-T interval, late coupled ventricular premature beats and long preceding cycles facilitate initiation of ventricular fibrillation in quinidine-treated patients; and (3) direct on-line monitoring should be utilized in the management of these patients.

Aged↗
PubMed1981

Myocardial dysfunction during paroxysmal supraventricular tachycardia.

Paroxysmal supraventricular tachycardia (PSVT) is associated with altered hemodynamics. We describe the echocardiographic features of myocardial dysfunction during a prolonged episode of PSVT in an 11-year-old male. The abnormality of the phases of cardiac activity presented as a markedly prolonged left ventricular systole (320 msec) and isovolumic relaxation phase (220 msec) and a shortened and delayed diastolic filling period (140 msec). These abnormalities reverted to normal immediately after spontaneous conversion to sinus rhythm. Propranolol, which was used to prevent PSVT in this child, may have been involved in the mechanism of the altered mechanical events.

Child↗