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Biomedical subjects

J A Abbott

Publications and source records attributed to J A Abbott.

At least 19 recordsLinked to original sources
PubMed1992

Usefulness of adenosine in augmenting ventricular preexcitation for noninvasive localization of accessory pathways.

Adenosine was administered to test the hypothesis that it would maximize preexcitation and facilitate noninvasive localization of accessory pathways in 22 patients with suspected accessory pathway-mediated tachycardias. Twelve-lead electrocardiograms and 2-dimensional echocardiograms were recorded at baseline and during adenosine-augmented ventricular preexcitation to localize the accessory pathway. Phase analysis was performed on digitized 4-chamber and short-axis views using a first harmonic Fourier transformation. At baseline, 15 patients had manifest preexcitation. In 14 of these patients (93.3%), preexcitation became more prominent after adenosine. Four patients without preexcitation at baseline clearly had it after adenosine. In patients who had preexcitation in response to adenosine, the electrocardiogram correctly identified the accessory pathway locations in 18 of 19 patients at a regional level and was incorrect in 1 of 19 patients. Echocardiographic phase analysis correctly identified the accessory pathway location in all 17 patients, who had technically adequate studies, at a regional level. In conclusion, administration of adenosine accentuates preexcitation, allowing for more accurate electrocardiographic and echocardiographic accessory pathway localization.

Adenosine↗
PubMed1992

Determination of patch electrode position for the internal cardioverter-defibrillator by cine computed tomography and its relation to the defibrillation threshold.

Cardioverter-defibrillator implantation in 22 consecutive patients after aborted sudden cardiac death was followed by prospective determination of the correct anatomic position of epicardial patch electrodes by chest X-ray study and cine computed tomography; the data were compared with the defibrillation threshold obtained intraoperatively. Patch electrode position was qualitatively graded. Computed tomography improved the assessment as compared with X-ray study in 13 patients (59%), visualizing electrodes in relation to the underlying myocardial and vascular structures. Although the computed tomographic technique provided more precise visualization, its grading of patch position correlated as poorly as that of the X-ray study with the measured acute defibrillation threshold. Three-dimensional reconstruction by computed tomography made it possible to determine quantitatively left ventricular mass (free wall and septum) and the mass encompassed by the patch electrodes. The 34.6 +/- 13.7% (range 12.6 to 61.1%) of the left ventricular mass encompassed by both patch electrodes showed a linear relation to the defibrillation threshold (r = 0.64, p = 0.01). Differentiation of free wall and septal mass in these measurements revealed that the proportion of septal mass encompassed by patch electrodes correlated closely with the defibrillation threshold (r = -0.6, p = 0.019), whereas that of the free wall mass, although significantly larger (35.4 +/- 15.8 vs. 20.6 +/- 15.4 g, p = 0.007), did not. Thus, the position of epicardial patch electrodes could be reliably determined by computed tomography.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Two-dimensional echocardiographic phase analysis. Its potential for noninvasive localization of accessory pathways in patients with Wolff-Parkinson-White syndrome.

BACKGROUND: In patients with the preexcitation syndrome who are undergoing transcatheter or surgical ablation, accurate localization of accessory pathways is critical. Because preexcitation is known to alter ventricular activation sequence and result in focal areas with presystolic contraction, we investigated whether phase analysis applied to two-dimensional echocardiographic cine loops objectively identifies these focal areas and can be used to localize ventricular insertion sites of accessory pathways. METHODS AND RESULTS: We prospectively obtained phase images in 17 patients (11 males; age range, 11-35 years) during minimal preexcitation in normal sinus rhythm and during maximal preexcitation induced by right atrial pacing. A group of 11 normal subjects (six men; age range, 26-37 years) served as controls. Pathway locations predicted from phase imaging were compared with those predicted from routine 12-lead ECGs, from visual inspection of cine loop images, and from catheter-mounted electrode endocardial mapping. Cross-sectional views in a digital cine loop format were mathematically transformed using a first harmonic Fourier algorithm to obtain the corresponding phase images. Phase angle histograms were derived in eight wall segments. Mean and earliest phase angles were derived by computer analysis to quantitate contraction sequence. We found that during right atrial pacing, phase angles in focal areas markedly deviated from normal--mean phase angles from 33 degrees to 164 degrees, and earliest phase angles from 50 degrees to 180 degrees. Accessory pathways could be precisely localized in 53% of the patients by 12-lead ECG, in 59% by visual inspection of cine loop images, in 82% by phase imaging, and in 94% by a combination of the three methods. CONCLUSIONS: Our results suggest that phase imaging, especially when used in combination with cine loop and 12-lead ECG, can be used to localize ventricular insertion sites of accessory pathways and may be clinically useful as a noninvasive adjunct to endocardial mapping in patients with Wolff-Parkinson-White syndrome.

Adult↗
PubMed1991

Relative importance of activation sequence compared to atrioventricular synchrony in left ventricular function.

This study evaluated the relative hemodynamic importance of a normal left ventricular (LV) activation sequence compared to atrioventricular (AV) synchrony with respect to systolic and diastolic function. Twelve patients with intact AV conduction and AV sequential pacemakers underwent radionuclide studies at rest and Doppler echocardiographic studies at rest and during submaximal exercise, comparing atrial demand pacing (AAI) to sequential AV sensing pacing (DDD) and ventricular demand pacing (VVI). Studies at rest were performed at a constant heart rate between pacing modes, and the exercise study was performed at a constant heart rate and work load. Cardiac output was higher during AAI than during both DDD and VVI (6.2 +/- 1 vs 5.6 +/- 1 and 5.3 +/- 1 liters/min, p less than 0.05). LV ejection fraction was likewise higher during AAI (55 +/- 12 vs 49 +/- 11 vs 51 +/- 13, p less than 0.05). VVI with or without AV synchrony was associated with a paradoxical septal motion pattern, resulting in a 25% impairment of regional septal ejection fraction. In addition, LV contraction duration was more homogenous during AAI. Peak filling rate during AAI and VVI was higher than during DDD (2.86 +/- 1 and 2.95 +/- 1 vs 2.25 +/- 1 end-diastolic volume/s; p less than 0.05). During VVI, the time to peak filling was significantly shorter than during both AAI and DDD (165 +/- 34 vs 239 +/- 99 and 224 +/- 99 ms; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmia, Sinus↗
PubMed1991

Left atrial volume determination by biplane two-dimensional echocardiography: validation by cine computed tomography.

Left atrial (LA) volume measurements have been made by the application of the method of discs (modified Simpson's rule) to orthogonal biplane atrial echocardiographic images. Validation of the technique has been suboptimal due to deficiencies of the reference standard, levophase angiography. To define the accuracy of echocardiography, we compared LA end-systolic volume by echocardiography in 27 patients with volumes by cine computed tomography (Cine CT), a highly accurate and validated method of measuring cardiac chambers. Echocardiographic tracings were made in the apical long-axis two- and four-chamber views. In patients with atria less than 300 ml, 14 had echoes performed prospectively, with optimization of LA size, while the remaining 10 were analyzed retrospectively. The volume of each slice was calculated and was then summated to obtain total volume. The correlation coefficient between two-dimensional echocardiography and Cine CT was r = 0.98, and it was r = 0.82 when patients with atria greater than 300 ml (n = 3) were excluded. Echocardiography underestimated Cine CT measurements by 23%. The slope of the prospective group was closer to unity than the slope of the retrospective group (p less than 0.001), and the correlation with Cine CT was slightly better for the prospective group (r = 0.88 versus r = 0.77). LA volume by two-dimensional echocardiography correlates closely with Cine CT, a more accurate method of volume determination, and gives valid measurements of LA volume. Efforts to maximize LA size during scanning limit inaccuracies of echocardiographic measurements of the left atrium.

Echocardiography↗
PubMed1991

Phase image triangulation of accessory pathways in patients undergoing catheter ablation of posteroseptal pathways.

The outcome of posteroseptal accessory pathway ablation by direct current (DC) shocks delivered just outside the os of the coronary sinus was studied in 21 patients. Electrocardiographic and electrophysiological parameters as well as phase image patterns of equilibrium multiple-gated blood-pool scintigrams were studied to determine their usefulness in predicting the success of ablation. A second free-wall pathway was documented by electrophysiological or surgical findings in six patients, and the value of phase images in detecting this second pathway was studied as well. Ablation was successful in 57%. The cumulative mean energy of DC shocks amounted to 524 +/- 170 joules and was not predictive of ablation outcome, neither was the mean ventriculoatrial (VA) conduction time. The predictive value of the 12-lead maximally preexcited electrocardiogram was poor in the 15 patients with a single posteroseptal bypass tract. A new method to triangulate the site of the earliest phase angle on the atrioventricular (AV) valve plane successfully localized the bypass pathway in 14 of those patients. No specific phase pattern predicted successful ablation except for a symmetrical, concentric peripheral phase progression found to be predictive of ablation success in the four patients who showed this pattern. Phase analysis was able to localize the second, nonposteroseptal pathway in four of six patients. This study showed that a concentric peripheral phase progression in the gated blood-pool scintigrams is predictive for ablation success in patients with posteroseptal pathways. A free-wall localization of the earliest phase angle is suggestive of a second bypass tract in this area.

Adolescent↗
PubMed1978

Cardiovascular trauma from angiographic jets--validation of a theoretic concept in dogs.

The relationship of angiographic injections to cardiovascular trauma was determined. The aorta of dogs was studied by a mathematic model that (a) defines the kinetic energy of contrast-media jets emanating from the exit holes of catheters and (b) enables precise correlation of energy levels to potential trauma. A universal curve independent of the Reynolds number of the jet readily determines how far the jet penetrates intravascular blood. A traumatic histopathologic spectrum was found for those injections predicted by the model to be traumatic. The curve enables the angiographer to calculate the safe operating range of any catheter.

Angiography↗
PubMed1978

Cardiac trauma from angiographic injections. A quantitative study.

To relate angiographic injections to potential cardiac trauma, we verified a mathematic theory that allows quantitative definition of the kinetic energy content of contrast jets emanating from the exit holes of angiographic catheters. Cineangiographic recordings of a range of jets of known energy content were obtained in 18 cardiac canine experiments and energy content and dissipation were quantified precisely from center line to jet edge. All contrast jets produced in clinical angiographic practice were turbulent, even those from hand injections into the coronary arteries. Energy content was related to an estimated cardiac wall damage threshold. At energy levels and damage thresholds predicted by the theory and computations, a traumatic spectrum was found by cineradiology and microscopic examination. A unique curve independent of jet Reynolds number was discovered relating the penetration of the contrast jet into the intravascular blood to the potential for cardiac trauma. This curve allowed ready calculation of hydraulic energy dissipation for any clinically used angiographic catheter and the definition of safe operational injection flow rates. Thus potential cardiac trauma can be anticipated and prevented.

Angiography↗
PubMed1978

Late sequelae of penetrating cardiac wounds.

Physiological and psychological parameters of 20 survivors of penetrating wounds of the heart were examined 7 to 52 months after recovery. All survivors had cardiac complaints. The psychological parameters for hypochondriasis, compulsiveness, and internalization were much greater in the patients than in control subjects but were similar to those in victims of violent major abdominal trauma. Physiological abnormalities were present in 19, although no particular pattern or abnormality could be related with certainty to the type of wound, operative procedure, or postoperative course. One recovered and re-employed victim required late surgical repair of a traumatic ventricular septal defect and ventricular diverticulum. Although functional work capacity measured by stress testing was normal in 90 percent, only eight survivors resumed employment. Complete rehabilitation was impaired by a residual traumatic neurosis. Management goals for patients with penetrating cardiac wounds should be broadened to include prevention of psychological disabilities.

Adult↗
PubMed1978

Electrophysiologic testing in patients with sinus pauses and/or sinoatrial exit block.

28 symptomatic patients with documented episodes of sinus pauses and/or sinoatrial exit block underwent electrophysiologic study. Abnormal responses to electrophysiologic testing were observed in 23/28 patients (82%). Abnormal prolongation of the maximum sinus node recovery time (SNRT max) occurred in 17/28 (61%) patients, of postpacing cycles 2.10 (secondary pauses) occurred in 21/28 (75%), and of estimated sinoatrial conduction time occured in 15/28 (54%). The incidence of abnormal responses to rapid atrial pacing (prolonged SNRT max or secondary pauses) (22/28, 79%) was higher than the incidence of abnormal responses to premature atrial stimulation (15/28, 54%) (P less than 0.005). Life-threatening cardiac arrhythmias were observed, prior to electrophysiologic study, in 5 out of 28 (18%) patients. Symptomatic patients with sinus pauses and/or sinoatrial exit block frequently (23/28, 82%) showed abnormal responses to electrophysiologic testing and have a relatively high incidence of life-threatening arrhythmias.

Adult↗
PubMed1977

A quantitative method for determining angiographic jet energy forces and their dissipation: theoretic and practical implications.

Jets emanating from the exit holes of cardiac catheters during angiographic injections are theoretically capable of producing severe localized cardiovascular trauma. We adopted a fluid mechanical model of an axially symmetric jet to define these energy forces quantitatively, especially as they would occur in the clinical setting. During angiographic injection at all catheter flow rates used clinically, the jet emanating from the exit hole was always turbulent. The physical characteristics of the turbulent jet penetration into the intravascular blood fell upon a universal curve independent of the jet Reynolds number. This curve, never previously described, allows ready calculation of hydraulic energy dissipation for any catheter of known length and lumen size. The diameter of the catheter exit orifice has a greater effect than injection flow rate on decreasing jet penetration. These results provide useful guidelines for reducing trauma during routine angiography.

Angiocardiography↗
PubMed1977

Graded exercise testing in patients with sinus node dysfunction.

Serial measurements of heart rate and oxygen uptake were obtained before and during maximal upright graded bicycle stress testing in 16 patients, 10 to 77 years old (mean 46 years), with sinus node dysfunction; five had permanent and two had temporary demand ventricular pacemakers. In 15 patients, including those with pacemakers, maximal exercise was performed before and after the intravenous administration of 1 mg atropine. Maximal exercise was terminated because of cerebral symptoms in seven (three had effort-induced tachyarrhythmias and one had autonomic insufficiency), fatigue in five (one had effort-induced heart block), heart failure in three and angina pectoris in one. With maximal exercise, patients with sinus node dysfunction were unable to obtain maximal heart rates or oxygen uptakes comparable to age- and sex-matched control subjects. Additionally, maximal oxygen uptake did not differ significantly between patients with or without pacemakers even when ventricular pacing rates were increased (two instances). The administration of atropine increased the resting heart rate, but the maximal heart rate and oxygen uptake achieved during maximal exercise did not differ significantly from those obtained before the administration of atropine in the patient and control groups. Physically active patients with sinus node dysfunction have diminished exercise capacity due in part to cardiac arrhythmia, latent or overt cardiac failure, or autonomic dysfunction.

Adolescent↗
PubMed1977

Graded treadmill stress testing. Patterns of physician use and abuse.

Treadmill stress testing is used in assessing the condition of patients with known or suspected heart disease. We did a prospective study to clarify physician ordering and integration of the test. Ordering criteria were always complied with, although most tests were ordered for evaluation of atypical chest pain and only a few for high risk patients with known cardiac dysfunction, indicating a misplaced emphasis on the diagnostic capabilities of the test. Tests in patients with atypical chest pain and stress-induced ischemic changes were always integrated, but in 30 percent of patients with atypical pain and no stress-induced electrocardiographic changes, the tests were not used in patient management. This was often due to the misconception that negative findings on a stress test excluded coronary disease. Physicians should be alerted to this misplaced emphasis and misconception.

California↗