PubMed Health⌕ Search

Biomedical subjects

D M Cassidy

Publications and source records attributed to D M Cassidy.

At least 19 recordsLinked to original sources
PubMed1991

Periodicity of global ventricular activation of sinus beats in patients with coronary artery disease and sustained ventricular tachycardia.

Despite increasing clinical reliance on signal-averaged electrocardiograms for determining risk for development of sustained ventricular tachycardia (VT), the periodicity of global ventricular activation during sinus rhythm has not been defined. Accordingly, epicardial and transmural ventricular electrograms during 6 consecutive sinus beats were evaluated in 10 patients with abnormal signal-averaged electrocardiograms who were undergoing surgery for VT. Bipolar electrograms were recorded with sock and needle electrodes from up to 96 epicardial and 156 transmural sites. Electrogram morphology, duration and activation were compared on a beat-to-beat basis. In all, 9,816 electrograms were analyzed. Mean durations of epicardial and transmural electrograms were 33 +/- 16 ms (range 6 to 199) and 23 +/- 10 ms (range 6 to 72), respectively, with a beat-to-beat variation of 1.9 +/- 1.4 ms per site. Similarly, local activation times did not vary significantly during the 6 cardiac cycles analyzed (mean variation 1.7 +/- 2.0 ms). Local conduction failure was not observed. Although electrograms during the terminal 40 ms of the QRS were significantly longer (36 +/- 20 vs 26 +/- 12 ms, p less than 0.001) when compared with those recorded earlier during the QRS complex, beat-to-beat variation in duration (2.1 +/- 1.6 ms) and activation (1.7 +/- 2.3 ms) was not significant. Results demonstrate that epicardial and transmural electrograms recorded during sinus rhythm in patients with sustained VT are periodic signals and thus establish a physiologic basis for signal averaging of electrocardiographic waveforms in these patients.

Aged↗
PubMed1990

Transmural ventricular activation during consecutive cycles of sustained ventricular tachycardia associated with coronary artery disease.

Although computerized mapping has enabled the intraoperative delineation of global ventricular activation from a single complex of ventricular tachycardia (VT), beat-to-beat reproducibility of isochronic maps has not been defined. To determine the reliability of single-beat analysis, epicardial and transmural ventricular electrograms during 6 consecutive VT cycles were analyzed in 10 patients during intraoperative mapping of sustained monomorphic VT. Bipolar electrograms were recorded simultaneously using sock and needle electrodes from up to 96 epicardial and 156 transmural sites. In each patient, at each electrode site, local activation time, electrogram duration and morphology were compared over 6 consecutive beats. A total of 9,816 electrograms were analyzed. For each patient, the isochronic activation map during VT was reproducible. Mean beat-to-beat variations in local epicardial and transmural activation times were only 1.7 +/- 1.7 and 2.04 +/- 1.9 ms, respectively (difference not significant). Moreover, electrogram duration did not vary significantly. Mean variations in epicardial and transmural electrogram durations were 2.1 +/- 1.8 and 1.4 +/- 1.9 ms, respectively (difference not significant). There were only 2 instances of 2:1 conduction failure; both occurred intramurally and adjacent to a site of VT origin. Thus, transmural ventricular activation during sustained monomorphic VT is reproducible regardless of electrode site or electrogram duration. These results demonstrate that analysis of a single beat of VT is a reliable and expedient method to delineate ventricular activation during intraoperative computerized mapping for the purpose of clinical decision-making in patients with sustained monomorphic VT.

Aged↗
PubMed1989

Capillary column gas chromatography-mass spectrometry for the determination of the fatty acid composition of human adipose tissue.

A procedure for determining the fatty acid composition of human adipose tissue using gas chromatography-mass spectrometry was developed. Adipose tissue was obtained from the lateral upper aspect of the right thigh by needle biopsy and prepared for analysis by lyophilisation, total lipid extraction and base-catalysed transesterification of the complexed fatty acids to form fatty acid methyl esters. Capillary column gas chromatography resolved thirty different peaks, ranging in carbon length from 12 to 24. Provisional identification of the peaks was by cochromatography with authentic standards and confirmed by gas chromatography-mass spectrometry using electron-impact ionisation. Fatty acid methyl esters were quantified in absolute amounts with respect to dry tissue weight and as a percentage of the total fat. Statistical analysis of the results from twenty healthy subjects using the two-tailed unpaired Student's t-test demonstrated women had significantly higher levels of myristoleic and palmitoleic acids (p less than 0.001) and lower levels of palmitic acid (p less than 0.05) in adipose tissue when compared with the male group. Similarly total saturated fatty acids was lower (p less than 0.05) and total monounsaturated fatty acids was higher in women than in men.

Adipose Tissue↗
PubMed1989

Within-clinic reagent strip lipid measurement.

The agreement between the Reflotron dry chemistry analyser and laboratory methods for measurement of total cholesterol and triglycerides was assessed by studying the between-method variability for individual samples. A paired comparison of replicate measurements from venous blood was made for 105 cholesterol and 90 triglyceride specimens. There was no significant mean difference between the two methods for cholesterol measurement (difference 0.02 mmol l-1, 95% Cl -0.07 to 0.10 mmol l-1) but there were wide limits of agreement (+/- 2SD) of -0.87 to 0.90 mmol l-1. Some of the differences in measurement were large enough to be clinically misleading and would result in inconsistencies in diagnostic assignment between the two methods. Both methods achieved relatively poor repeatability which limited the agreement possible (coefficient of repeatability, defined as 2SD of the differences, 0.59 mmol l-1 for the Reflotron and 0.38 mmol l-1 for the laboratory). The repeatability of triglyceride measurement was similar for the Reflotron and laboratory (coefficient of repeatability 0.24 mmol l-1 and 0.27 mmol l-1, respectively). However, there was a significant systematic difference between methods, with the Reflotron reading 0.30 mmol l-1 less than the laboratory method (95% Cl 0.26 to 0.35 mmol l-1) and the limits of agreement between the methods were -0.09 to 0.70 mmol l-1. It is important that clinicians recognize the limits of agreement between dry chemistry analysers and laboratory methods and take these into account when using them to screen for hyperlipidaemia or to monitor treatment of hyperlipidaemic diabetic patients.

Cholesterol↗
PubMed1989

Sinus mapping in patients with cardiac arrest and coronary disease--results and correlation with outcome.

Electrophysiological testing and left ventricular endocardial mapping in sinus rhythm were performed in 61 patients with coronary artery disease who presented with cardiac arrest in an attempt to relate the results of these studies to clinical outcome. Forty-one patients (67%) had inducible sustained arrhythmias (18 uniform ventricular tachycardia, 23 polymorphic ventricular tachycardia/ventricular fibrillation) and 20 had no inducible arrhythmia. Patients with inducible arrhythmia had 45% abnormal and 6% fractionated electrograms versus 31% and 0% for those without inducible arrhythmia (P greater than 0.05 for both comparisons). Sixteen of 59 patients (27%) with adequate follow-up had arrhythmia recurrence (11/39 [31%] with inducible arrhythmia and 5/20 [25%] without inducible arrhythmia) over a mean follow-up period of 27 months. Of five patients without inducible arrhythmia who experienced recurrence, two did so despite the anti-ischemic therapy. In the 20 patients without inducible arrhythmia, the 15 who remained arrhythmia-free had a mean of 78 +/- 22% normal sites versus 46 +/- 24% normal sites in those with recurrence (P greater than 0.05). We conclude that in patients with coronary artery disease and cardiac arrest: 1) patients without inducible arrhythmia have less marked endocardial electrical abnormality than those with inducible arrhythmia, 2) those patients who have marked endocardial abnormality despite the lack of inducible arrhythmia are at risk for clinical recurrence which suggests that these abnormalities may represent an anatomic substrate for arrhythmia which cannot be identified by programmed stimulation. These patients are candidates for AICD implantation and 3) patients with relatively normal endocardial electrograms do well with anti-ischemic therapy alone.

Aged↗
PubMed1988

Anterior left ventricular aneurysm: factors associated with the development of sustained ventricular tachycardia.

Fifty patients with anteroapical left ventricular aneurysm secondary to prior myocardial infarction underwent aneurysmectomy, at which time endocardial sinus rhythm mapping was performed. Forty patients had a history of recurrent sustained monomorphic ventricular tachycardia, and 10 had an aneurysm but no history of spontaneous sustained tachycardia. A comparison of the clinical, angiographic and sinus rhythm endocardial electrographic characteristics of these two groups revealed that the patients without spontaneous ventricular tachycardia had more severe coronary artery disease (2.6 +/- 0.5 versus 1.9 +/- 0.8 coronary arteries having greater than 70% stenosis; p less than 0.03), underwent surgery earlier after infarction (3 +/- 2 versus 46 +/- 53 months; p less than 0.03) and had less extensive wall motion abnormalities on contrast ventriculography (0 of 8 versus 13 of 35 patients assessed had an abnormally contracting ventriculographic segment length greater than 60%; p less than 0.04). During intraoperative programmed electrical stimulation, all 40 patients with and 4 of 10 without a history of spontaneous ventricular tachycardia had inducible tachycardia. The patients with inducible tachycardia had a larger area of endocardium from which abnormal electrograms (duration greater than 70 ms or amplitude less than 0.7 mV) were recorded (62 +/- 17 versus 45 +/- 20% of electrograms; p less than 0.03) as well as fractionated (duration greater than 90 ms, amplitude less than 0.3 mV) electrograms (20 +/- 14 versus 9 +/- 7% of electrograms; p less than 0.04) than did patients without inducible tachycardia, but there were no angiographic differences between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Pacing, Artificial↗
PubMed1988

Nonuniform recovery of excitability in the left ventricle.

The purpose of this study was to determine left ventricular activation, dispersion of refractoriness, and total recovery time in patients with coronary artery disease and ventricular tachycardia and in patients with the long QT syndrome and to compare these patients with a group of normal patients. Left ventricular endocardial catheter mapping and left ventricular refractory period determination were performed in 18 patients. Group 1 consisted of seven patients with no heart disease and no arrhythmia; group 2 consisted of six patients with previous infarction and sustained ventricular tachycardia; and group 3 consisted of five patients with prolonged QT interval and previous cardiac arrest. Total left ventricular endocardial activation was significantly longer in group 2 (75 +/- 23 msec, mean +/- SD) compared with group 1 (34 +/- 9 msec, p less than 0.01) and group 3 (42 +/- 5 msec, p less than 0.05). Dispersion of refractoriness was significantly greater in group 3 (87 +/- 27 msec) than in group 1 (40 +/- 14 msec, p less than 0.01) and group 2 (53 +/- 14 msec, p less than 0.05). Dispersion of total recovery time was significantly greater in group 2 (90 +/- 30 msec) than in group 1 (52 +/- 14 msec, p less than 0.05) as well as group 3 (114 +/- 43 msec) compared with group 1 (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Effects of tetracyclic antidepressant drugs on the electrophysiological properties of canine cardiac Purkinje fibres.

The direct actions of the tetracyclic antidepressant drugs maprotiline and mianserin on isolated, superfused, canine cardiac Purkinje fibres were examined in vitro using glass microelectrode recordings and programmed stimulation. Purkinje fibre bundles were driven at 1.25 Hz and electrophysiological measurements were made before and 40 mins after addition of maprotiline or mianserin to the perfusate in a concentration of 50, 250 or 1000 ng/mL. In nondepressed Purkinje fibres maprotiline but not mianserin caused slight resting hyperpolarization at 50 ng/mL while neither drug affected resting membrane potential at the higher concentrations. Maprotiline but not mianserin caused dose-related reductions of action potential amplitude, maximal upstroke velocity of phase 0 (Vmax) and conduction velocity; and both drugs reduced action potential duration and effective refractory period. In depressed fibres mianserin alone was tested at concentrations of 250 and 1000 ng/mL, and was again found to have no effect on resting membrane potential, amplitude, Vmax or effective refractory period although it did reduce action potential duration by 17% and conduction velocity by 19%. Thus, the direct cellular electrophysiological actions of maprotiline resembled those reported for the tricyclic anti-depressants. The weak or absent depressant effects of mianserin on amplitude, Vmax and conduction velocity distinguish this drug from maprotiline and the tricyclic anti-depressants and may explain the low incidence of toxic ventricular arrhythmias and conduction disturbances associated with the clinical use of mianserin.

Action Potentials↗
PubMed1986

Abnormalities of endocardial activation pattern in patients with previous healed myocardial infarction and ventricular tachycardia.

Endocardial catheter mapping was performed in 27 patients with anterior wall acute myocardial infarction (AMI) and in 10 patients with inferior wall AMI. All patients had a history of ventricular tachycardia. Left ventricular breakthrough occurred at 10 +/- 4 ms after the QRS complex in inferior AMI and 11 +/- 7 ms after the QRS complex in anterior AMI. Total electrical activity recorded during sinus rhythm was 164 +/- 46 ms in inferior and 144 +/- 28 ms in anterior AMI (p = 0.05). Nine of the 10 patients with inferior AMI had complete activation of the anterior wall within the initial one-half of the QRS complex, compared with only 15 of the 27 patients with anterior AMI (p = 0.05). All 10 patients with inferior AMI had activation of the ventricular septum within the initial half of the QRS complex compared with only 13 of 27 with anterior AMI (p less than 0.005). None of the patients with inferior AMI had activation of the inferoposterior base within the initial one-half of the QRS complex, compared with 21 of 27 patients with anterior AMI (p less than 0.001). Complete activation of the anterior wall occurred at 33 +/- 15 ms in inferior and 58 +/- 30 ms in anterior AMI (p less than 0.005). Complete activation of the septum occurred at 38 +/- 12 ms in inferior and 63 +/- 28 ms in anterior AMI (p less than 0.005). Complete activation of the inferoposterior base occurred at 100 +/- 38 ms in inferior and 50 +/- 21 ms in anterior AMI (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Lipogenesis in isolated human sebaceous glands.

Lipogenesis in isolated human sebaceous glands from [U-14C]glucose, [U-14C]leucine, [U-14C]isoleucine, and [U-14C]valine has been determined by thin-layer chromatography. Total lipogenesis from 2 mmol/l [U-14C]glucose was 114.8 +/- 22.3 pmol/gland per h (mean +/- SE), with 53.8% being incorporated into triglycerides, 20.2% into squalene, 12.8% into phospholipids, 2.1% into cholesterol and 7.1% into wax monoester and cholesterol ester and 5% into di- and monoglycerides and free fatty acids. Total lipogenesis from 2 mmol/l [U-14C]leucine, 2 mmol/l [U-14C]isoleucine, and 2 mmol/l [U-14C]valine in the presence of 2 mmol/l glucose was 26, 29 and 9%, respectively, of that seen with 2 mmol/l glucose alone. The pattern of 14C distribution in the various lipid classes from the three U-14C-labelled branched-chain amino acids was not significantly different from that seen with [U-14C]glucose.

Carbon Radioisotopes↗
PubMed1986

Left ventricular endocardial activation during right ventricular pacing: effect of underlying heart disease.

Endocardial catheter mapping of the left ventricle was performed in 40 patients during right ventricular pacing to determine the effect of underlying myocardial infarction on endocardial activation. Group I comprised 18 patients without infarction, Group II 12 patients with inferior infarction and Group III 10 patients with anteroseptal infarction. Thirty-nine of the 40 patients had only a single left ventricular breakthrough site located on the midseptum in 33 cases, apical septum in 4 cases and basal septum in 2 cases. The earliest left ventricular local activation time during right ventricular pacing was earlier in Group III (40 +/- 11 ms) than in Group I (55 +/- 17 ms) and Group II (60 +/- 15 ms) (p less than 0.01). Total endocardial activation time was significantly longer in Group III (118 +/- 30 ms) than in Group I (76 +/- 14 ms) and Group II (72 +/- 20 ms) (p less than 0.001). The latest left ventricular site of activation during right ventricular pacing was the inferoposterior base in 14 (77%) of the 18 Group I patients, and 10 (83%) of the 12 Group II patients. The latest site of activation in Group III patients was variable. It is concluded that: left ventricular endocardial activation patterns and conduction times are influenced by the site of previous infarction. Longer total endocardial activation in Group III suggests that specialized conducting tissue in the septal and anterior walls may play an important role in left ventricular activation during right ventricular pacing.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Pacing, Artificial↗
PubMed1986

Endocardial catheter mapping in patients in sinus rhythm: relationship to underlying heart disease and ventricular arrhythmias.

Catheter mapping during sinus rhythm was performed in 132 patients with coronary artery disease and 26 patients with congestive noncoronary cardiomyopathy. Each of the patients had a clinical history of one of the following: no ventricular arrhythmia, nonsustained ventricular tachycardia, cardiac arrest, or sustained ventricular tachycardia. The characteristics of the endocardial electrogram and other measured indexes of slow endocardial conduction were compared between patients with different types of disease and in different arrhythmia groups to determine if differences existed. The cardiomyopathic group had a higher percent of normal endocardial electrograms than the coronary artery disease group, with no evidence of slow endocardial conduction. The sustained ventricular tachycardia group exhibited a greater percent of abnormal endocardial electrograms and more evidence of slow endocardial conduction, distinguishing this group from the three other arrhythmia groups. We conclude the following: The underlying electrophysiologic substrate varies in patients with different ventricular arrhythmias. It is therefore inappropriate to analyze all patients with ventricular arrhythmias as a single group. Patients with congestive noncoronary cardiomyopathy, regardless of the type of their arrhythmia, have a relatively normal endocardium. Those patients with serious ventricular arrhythmias should not be considered candidates for surgery directed at removing abnormal endocardium.

Aged↗
PubMed1985

Electrophysiologic evaluation and follow-up characteristics of patients with recurrent unexplained syncope and presyncope.

One hundred nineteen patients with unexplained syncope (82%) or presyncope (18%) underwent complete electrophysiologic study (EPS). Symptoms were recurrent in 72% of the patients. Fifty-two percent of the patients had structural heart disease. Forty-one patients had normal EPS results and 78 had electrophysiologic abnormalities (ventricular tachycardia in 31, induced atrial flutter/fibrillation in 17, vasovagal syncope in 8, hypersensitive carotid sinus syndrome in 7, supraventricular tachycardia in 6, heart block in 5 and sick sinus syndrome in 4). The presence of structural heart disease (p = 0.0033) and previous myocardial infarction (p = 0.05) were the only clinical or electrocardiographic predictors of a positive EPS response. Therapy was guided by EPS and patients were followed for 27 +/- 20 months (mean +/- standard deviation). In the patients with negative EPS results, 76 +/- 11% (mean +/- standard error) were symptom-free at follow-up, compared to 68 +/- 10% in the group with positive EPS responses. No clinical variables helped to predict remission in the absence of therapy. One patient in the negative EPS response group and 2 patients in the EPS positive group died suddenly (cumulative survival 94 +/- 4%). Total cardiovascular mortality was 13% in the positive EPS response group, and 4% in the negative EPS response group. Thus, certain clinical characteristics are helpful in selecting patients for study. Electrophysiologically guided therapy is associated with a recurrence and sudden death rate similar to an untreated control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Catheter mapping during sinus rhythm: relation of local electrogram duration to ventricular tachycardia cycle length.

Catheter mapping was performed during sinus rhythm in 52 patients with 102 morphologically distinct ventricular tachycardias (VT). Twenty patients had a single VT morphologic pattern. The cycle length of VT was correlated with the duration of all electrograms and various electrogram subgroups, including abnormal, fractionated, late, and longest electrograms, as well as the electrogram recorded at the site of origin of VT and at sites other than the site of origin using linear regression analysis. No correlation was found between local electrogram duration of any of these groups and VT cycle length. There was no relation regardless of whether the patient had a single or multiple morphologic patterns. Thus, the local electrogram duration measured with catheter mapping during sinus rhythm does not correlate with VT cycle length. This finding provides additional support that catheter mapping during sinus rhythm does not give sufficient information to guide localized endocardial resection for VT surgery.

Electrocardiography↗
PubMed1985

Use of programmed electrical stimulation to predict sudden death after myocardial infarction.

The use of programmed ventricular stimulation to identify patients at risk for sudden cardiac death following myocardial infarction has not yet been firmly established. The repetitive ventricular response following extrastimuli does not appear to be useful in identifying patients at risk and should not be used to guide antiarrhythmic therapy. Similarly, the response to single and/or double ventricular extrastimuli delivered at twice diastolic threshold from a single right ventricular site during normal sinus rhythm and ventricular pacing also does not appear to be helpful in identifying patients at risk for life-threatening ventricular arrhythmias. A more vigorous stimulation protocol that involves more than one right ventricular site and increased current strength may be necessary to elicit a predictive electrophysiologic response. The need for a more vigorous stimulation is suggested by two preliminary studies. Confirmation of initial reports is necessary. The predictive value of the response to programmed ventricular stimulation must be compared with other noninvasive and invasive measurements of left ventricular dysfunction and the degree of spontaneous ventricular ectopy to determine its superiority or to ascertain multiple variables that can be used together to identify those patients most likely to die suddenly after myocardial infarction. Stimulation protocols used during programmed stimulation must have sufficient sensitivity without sacrificing specificity. A concerted effort using uniform stimulation protocols in large numbers of patients is essential to resolve this important clinical problem.

Cardiac Pacing, Artificial↗
PubMed1984

Repetitive, monomorphic ventricular tachycardia: clinical and electrophysiologic characteristics in patients with and patients without organic heart disease.

The clinical and electrophysiologic characteristics of 6 patients who had repetitive monomorphic ventricular tachycardia (VT) after a remote myocardial infarction (group A) were compared with those of 22 patients who had this arrhythmia without structural heart disease (group B). VT had a right bundle branch block morphologic pattern in 5 of 6 group A patients and a left bundle branch block morphologic pattern in all group B patients. Endocardial catheter activation mapping was performed in 4 group A patients and in 9 group B patients during VT. In all group A patients, the site of VT origin was on the border of the previous infarction; in all group B patients VT originated at the right ventricular outflow tract. Pacing and programmed stimulation induced VT in 5 of 6 group A patients and 7 of 22 group B patients (p = 0.03). Isoproterenol infusion provoked VT in 4 group A patients and 9 group B patients. Type I antiarrhythmic agents suppressed VT in 4 group A patients and in 14 group B patients, whereas propranolol suppressed VT in 3 of 3 group A patients tested and in 12 of 20 group B patients. Verapamil suppressed spontaneous VT in 1 group A patient and in 4 group B patients. During a mean follow-up of 19 months for group A and 40 months for group B, no patient had died suddenly or had cardiac arrest.

Adolescent↗