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Biomedical subjects

B G Denys

Publications and source records attributed to B G Denys.

At least 19 recordsLinked to original sources
PubMed1995

Predisposing risk factors and natural history of acute neurologic complications of left-sided cardiac catheterization.

The reported incidence of acute neurologic complications of left heart catheterization varies from 0.03% to 0.3%. The predisposing risk factors, clinical features, and natural history have not been well characterized. We retrospectively reviewed all cases of acute neurologic complications developing during or within 36 hours of diagnostic catheterization or angioplasty to determine the incidence, clinical features, and natural history, and (using a case-control methodology) the clinical variables associated with their development. During the 37-month study, 6,465 patients underwent diagnostic left-sided cardiac catheterization and balloon angioplasty or valvuloplasty, and 27 patients developed an acute neurologic complication (0.4%). The most common symptoms were visual disturbances (26%), hemiparesis (26%), and facial droop (26%). Deficits were localizable to the anterior or posterior circulation in 22 patients: posterior in 8 (36%), and anterior in 14 (64%). Long-term follow-up was available in all patients, with 17 of 27 (63%) having complete resolution with no residuum. With use of a case-control methodology and multiple logistic regression analysis, female gender, the presence of left ventricular hypertrophy, depressed ejection fraction, and the presence of > or = 2 coronary arteries with > 50% narrowing were independent predictors of a neurologic event.

Acute Disease↗
PubMed1995

Endogenous opioids may modulate catecholamine secretion during high intensity exercise.

To determine the effect of endogenous opioids on catecholamine response during intense exercise [80% maximal oxygen uptake (VO2max)], nine fit men [mean (SE) VO2max, 63.9 (1.7) ml.kg-1.min-1; age 27.6 (1.6) years] were studied during two treadmill exercise trials. A double-blind experimental design was used with subjects undertaking the two exercise trials in counterbalanced order. Exercise trials were 20 min in duration and were conducted 7 days apart. One exercise trial was undertaken following administration of naloxone (N; 1.2 mmol.l-1; 3 ml) and the other after receiving a placebo (P; 0.9% saline; 3 ml). Prior to each experimental trial a flexible catheter was placed into an antecubital vein and baseline blood samples were collected. Immediately afterwards, each subject received bolus injection of either N or P. Blood samples were also collected after 20 min of continuous exercise while running. Epinephrine and norepinephrine were higher (P < 0.05) in the N than P exercise trial with mean (SE) values of 1679 (196) versus 1196 (155) pmol.l-1 and 24 (2.2) versus 20 (1.7) nmol.l-1, respectively. Glucose and lactate were higher (P < 0.05) in the N than P exercise trial with values of 7 (0.37) versus 5.9 (0.31) mmol.l-1 and 6.9 (1.1) versus 5.3 (0.9) mmol.l-1 respectively. These data suggest an opioid inhibition in the release of catecholamines during intense exercise.

Adult↗
PubMed1994

Automatic detection of ventricular tachycardia and fibrillation using ECG processing and intramyocardial pressure measurement.

Ventricular electrograms and intramyocardial pressure signals were recorded in 11 dogs during sinus rhythm, during paced ventricular tachycardia, and at the onset of and during ventricular fibrillation. The autocorrelation function and the probability density function of short episodes of the electrograms were analyzed off-line on a digital computer. Peak-to-peak values of the intramyocardial pressure were calculated during sinus rhythm and during ventricular tachycardia and fibrillation. An algorithm was developed to recognize tachycardia and fibrillation using the autocorrelation function, the probability density function, and the intramyocardial pressure as input signals. Results show that in case of sinus rhythm all detection methods are reliable (recognition rate of 100%). In case of ventricular tachycardia with hemodynamic impairment the autocorrelation function is slightly better (66.6%) than the probability density function (44.4%). The onset of ventricular fibrillation is sensed in 81.8% of all episodes with the autocorrelation function and in 63.6% with the probability density function. During ventricular fibrillation this improves, respectively, to 92.3 and 69.2%. In all previous cases the intramyocardial pressure signal was 100% reliable. It is concluded that in this arrhythmia model, the sensitivity of an automatic ventricular tachycardia/fibrillation detection system was increased by combining ECG processing with analysis of an hemodynamic parameter.

Algorithms↗
PubMed1991

Anatomical variations of internal jugular vein location: impact on central venous access.

OBJECTIVE: To evaluate whether underlying anatomical variations in the position of the internal jugular vein may account for difficulty in obtaining central venous access in individual patients. DESIGN: Consecutive series. SETTING: Cardiac catheterization laboratory, coronary care unit, and ICU. PATIENTS: Two hundred patients (52 +/- 7 yrs, 147 males) who were undergoing internal jugular vein cannulation for hemodynamic monitoring or endomyocardial biopsy. INTERVENTION: The internal jugular vein and carotid artery were visualized with two-dimensional ultrasound and their position was compared with their projected location from external landmarks. RESULTS: In 183 (92%) patients, the position of the internal jugular vein was lateral and anterior to the carotid artery and increased in diameter during a Valsalva maneuver. In five (2.5%) patients, the internal jugular vein was not visualized and was probably thrombosed, as the internal jugular vein was normal on the other side. In six (3%) patients, the internal jugular vein was unusually small and did not increase in diameter during the Valsalva maneuver. In two (1%) patients, the internal jugular vein was positioned greater than 1 cm lateral to the carotid artery. Four (2%) patients had a medially positioned internal jugular vein overlying the carotid artery. In 5.5% of the patients, the position of the internal jugular vein was outside the path that had been predicted by the external landmarks. CONCLUSIONS: These findings suggest that anatomical variation may partly account for the inability to cannulate the internal jugular vein in certain patients. In these cases, ultrasound examination quickly establishes the position of the internal jugular vein and may allow for easy and rapid access.

Carotid Arteries↗
PubMed1991

The use of ionic and nonionic contrast agents and the effects of hydration in the post cardiac transplant patient with moderate renal insufficiency.

To determine the effects of ionic (diatrizoate) and nonionic (iopamidol) contrast and of hydration, 90 asymptomatic cyclosporine-treated cardiac transplant patients with moderate renal insufficiency (serum creatinine greater than or equal to 1.5 mg/dL) undergoing cardiac catheterization were evaluated. All patients were hydrated with intravenous fluid (5% dextrose and 0.5 normal saline) over a twelve-hour period prior to catheterization and with oral fluids thereafter. Thirty patients received iopamidol (Group I) and 60 were given diatrizoate (Group II). Renal function was determined the day before and after catheterization in all patients of Group I and in 30 patients of Group II (Group IIa). In the remaining 30 patients of Group II renal function was also determined before contrast administration (Group IIb). The dose of dye was similar in all groups (I: 139 +/- 55 mL, IIa: 140 +/- 58 mL, IIb: 128 +/- 38 mL). There was a significant decrease in BUN (I: 41 +/- 10 to 33 +/- 8 mg/dL [p less than 0.005], IIa: 42 +/- 9 to 33 +/- 8 mg/dL mg/dL [p less than 0.001], IIb: (44 +/- 12 to 34 +/- 10 mg/dL [p less than 0.005]) and a small decrease in serum cratinine after catheterization (I: 2.0 +/- 0.3 to 1.9 +/- 0.3 mg/dL, IId: 2.0 +/- 0.3 to 1.9 +/- 0.3 mg/dL, IIb: 2.1 +/- 0.4 to 1.8 +/- 0.4 mg/dL [p less than 0.005].(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Urea Nitrogen↗
PubMed1987

Simultaneous right atrial appendage sensing with a target tip, a solid tip and J orthogonal electrodes.

To compare the sensing characteristics of a solid tip, target tip (Medtronic) and orthogonal electrodes within the right atrial appendage, atrial electrograms were simultaneously recorded from 2 pacing leads in 11 patients. No significant differences were noted between atrial electrograms derived from target tip or a solid tip electrode in contact with atrial myocardium. Mean values for P-wave amplitudes of 3.0 vs 3.1 mV and slew rates 0.4 V/s vs 0.6 V/s, and QRS amplitudes of 1.0 vs 1.2 mV and slew rates 0.4 vs 0.2 V/s were obtained. The frequency content was also similar, with spectral maxima at 8 vs 9 Hz (P wave) and 7 vs 6 Hz (QRS). In contrast, atrial electrocardiograms derived from the orthogonal electrodes were significantly different: P-wave amplitude of 6.1 mV (p less than 0.025) and slew rate of 1 V/s and QRS of 0.13 mV and slew rate of 0.04 V/s. Spectral analysis was also dissimilar with maxima at 34 Hz (P wave) and 3 Hz (QRS). Orthogonal noncontacting sensing electrodes positioned within the atrial appendage offer substantially better electrographic P-wave amplitude detection and QRS rejection than contacting tip electrodes. These leads yield a significant improvement when discriminate atrial sensing is required.

Atrial Function↗
PubMed1987

Sensing and pacing with floating electrodes in the right atrium and right atrial appendage.

Unipolar and bipolar floating atrial electrograms from 58 pacemaker patients were recorded and compared. Twenty-four floating unipolar electrodes and 29 floating bipolar electrodes were used at mid-right atrial level and five orthogonal atrial J leads within the right atrial appendage. Each signal was analyzed in the time domain: peak to peak deflection of P wave and QRS complex, duration of P wave and QRS complex and slew rate; and in the frequency domain: maximum of the energy spectrum and frequency at which a decrease of 3 dB from the maximal amplitude occurred. Atrial P (1.31 +/- 0.94 mV, mean +/- SD) and QRS (1.0 +/- 0.56 mV) waves from unipolar floating electrodes were comparable, whereas they were significantly different from bipolar floating electrodes (1.15 +/- 0.77 mV and 0.25 +/- 0.39 mV). Amplitudes of P waves from orthogonal J leads were largest (3.1 +/- 2.6 mV) and QRS complexes (0.21 +/- 0.13 mV) smallest. The P waves had the highest frequency content (17.1 +/- 19.4 Hz). It is concluded that atrial electrograms from orthogonal electrodes (bipolar or orthogonal J) offer superior sensing characteristics because of the large amplitude P wave and discriminating power between P and QRS waves (P/QRS voltage 15:1). An orthogonal J lead can thus be used for P synchronous pacing at the atrial level, whereas an orthogonal ventricular lead can be used for rate-response pacing systems.

Atrial Function↗
PubMed1986

Sensing characteristics of unipolar and bipolar orthogonal floating atrial electrodes: morphology and spectral analysis.

We investigated wave morphology and spectral energy distributions of signals picked up by floating atrial unipolar and bipolar orthogonal sensing electrodes. Our data show that atrial P and QRS waves from unipolar floating electrodes are comparable. On the other hand, atrial P and QRS waves from bipolar orthogonal floating electrodes are significantly different. Even at high and mid right atrial locations, QRS waves are either absent or much smaller in amplitude and lower in frequency content than P waves. We conclude that the bipolar orthogonal floating atrial electrode is superior to the unipolar one for sensing due to its P to QRS wave discriminating power, which makes complex input filters or algorithms unnecessary. Our data support the idea that physiologic pacing with a VDD or VAT pacemaker is possible using a single pass lead.

Electrocardiography↗
PubMed1986

Detection of ventricular tachycardia and fibrillation using ECG processing and intramyocardial pressure gradients.

The automatic termination of malignant tachyarrhythmias and of ventricular fibrillation by an implantable device requires a reliable sensing of these episodes of abnormal ECG. Therefore, we induced tachyarrhythmias and fibrillation in eleven dogs and recorded electrograms and intramyocardial pressure. The electrograms were analyzed using the autocorrelation function and the probability density function. Intramyocardial pressure was monitored as a hemodynamic parameter. Results show that in the case of sinus rhythm, all methods are reliable, but in the case of VT and VF, electrogram processing only is insufficient. It is concluded that combined monitoring of ECG processing and a hemodynamic parameter may increase the sensitivity of an automatic tachycardia-fibrillation detection system.

Animals↗
PubMed1986

Orthogonal atrial appendage sensing.

The characteristics of electrograms derived from a solid platinum-iridium pacing catheter tip in contact with the right atrial appendage are compared to those derived from a Target-tip electrode. Both are then compared to electrograms from two noncontacting orthogonal electrodes positioned more proximally within the atrial appendage. Wave form morphology and spectral energy distribution were determined for the three sets of electrograms. It is concluded that orthogonal electrodes placed within the atrial appendage may offer enhanced atrial sensing required by more sophisticated pacemakers.

Electrocardiography↗
PubMed1986

Relationship between left ventricular pressure and the calibrated apexcardiogram during abrupt outflow obstruction.

In order to study the influence of sudden left ventricular pressure rise on the calibrated apexcardiogram, 181 acute aortic occlusions were performed during systole in 7 dog experiments. For each beat preceding (CO) an occlusion and each occlusion (OC), peak systolic amplitude of left ventricular pressure (CO: 118.5 +/- 17.8 mm Hg; OC: 205.8 +/- 38.7 mm Hg) and apexcardiogram (CO: 48.8 +/- 16.7 mm Hg; OC: 63.0 +/- 25.8 mm Hg) were measured. Pressure gradients, ratios and surface areas of all tracings were digitally calculated. The cross-correlation function between pressure and apexcardiogram was also calculated in order to determine time lags. Significant correlations were found: between surface ratios and pressure gradient of pressure (r = 0.80, p less than 0.001) and of apexcardiogram (r = 0.79, p less than 0.001); between surface ratios of pressure and surface of apexcardiogram (r = 0.52, p less than 0.001). The data suggest that during isovolumic systole, the time integral of the left ventricular pressure and its change during the ejection phase define to a large extent the general shape and size of the apexcardiogram.

Animals↗
PubMed1985

Investigation of genesis of gallop sounds in dogs by quantitative phonocardiography and digital frequency analysis.

Several investigators have noted external gallop sounds to be of higher amplitude than their corresponding internal sounds (S3 and S4). In this study we hoped to determine if S3 and S4 are transmitted in the same manner as S1. In 11 closed-chest dogs, external (apical) and left ventricular pressures and sounds were recorded simultaneously with transducers with identical sensitivity and frequency responses. Volume and pressure overload and positive and negative inotropic drugs were used to generate gallop sounds. Recordings were made in the control state and after the various interventions. S3 and S4 were recorded in 17 experiments each. The amplitude of the external S1 was uniformly higher than that of internal S1 and internal gallop sounds were inconspicuous. With use of Fourier transforms, the gain function was determined by comparing internal to external S1. By inverse transform, the amplitude of the internal gallop sounds was predicted from external sounds. The internal sounds of significant amplitude were predicted in many instances, but the actual recordings showed no conspicuous sounds. The absence of internal gallop sounds of expected amplitude as calculated from the external gallop sounds and the gain function derived from the comparison of internal and external S1 make it very unlikely that external gallop sounds are derived from internal sounds.

Animals↗
PubMed1985

Intramyocardial pressure in the canine heart. An experimental study.

During 11 acute open-chest experiments with dogs, intramyocardial pressure was measured in the anterior wall of the left ventricle with a miniature pressure transducer mounted on a 1.6 mm diameter needle. Pressures were measured at the subendocardium (+/- 10 mm), midwall (+/- 7.5 mm), and subepicardium (+/- 5 mm). Simultaneous recordings of left ventricular pressure and two measures of intramyocardial pressure were made during control, acute volume overload, and after administration of verapamil. Maximal amplitude of the subendocardial pressure was higher and the maximal amplitude of the subepicardial pressure was lower than maximal left ventricular pressure for all interventions (p less than 0.001 and p less than 0.01). During volume overload left ventricular pressure increased more than intramyocardial pressure (left ventricular pressure 34%, subendocardial pressure 6%, midwall pressure 14%, and subepicardial pressure 14%). After the administration of verapamil intramyocardial pressure decreased more than left ventricular pressure (left ventricular pressure 16%, subendocardial pressure 26%, midwall pressure 13%, subepicardial pressure 32%). Positive and negative first derivatives of subendocardial pressure were higher than those of left ventricular pressure during control and after verapamil (between p less than 0.01 and p less than 0.001). Positive and negative first derivatives of subepicardial pressure were lower than those of left ventricular pressure during all interventions (p less than 0.001). The timing of the C-point (onset of mechanical contraction) and the positive first derivative of all tracings was synchronous within 8 msec in all interventions. The 0-point (crosspoint of the tangent to the diastolic plateau and the tangent to the relaxation slope; early diastole) of intramyocardial pressure came later than the 0-point of left ventricular pressure, indicating longer relaxation times in the myocardium (subendocardial pressure: control, p less than 0.001, volume, p less than 0.05, verapamil, no significance; midwall pressure: between p less than 0.05 and p less than 0.001; subepicardial pressure: between p less than 0.01 and p less than 0.001).

Animals↗