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Biomedical subjects

T M Bashore

Publications and source records attributed to T M Bashore.

153 records · Page 9Linked to original sources
PubMed1982

The epicardial screw-on electrode. An analysis of 114 consecutive patients with complete one-year follow-up.

This study assesses the clinical and electrode complications associated with the use of the epicardial screw-on electrode technique for permanent ventricular pacing. The records of 114 consecutive patients who received screw-on epicardial electrodes were analyzed in-hospital and at one year following implantation. We compared two techniques of implanting the screw-on electrode: 72 transmediastinal (TM) and 42 subxiphoid (SX) procedures. Baseline clinical inequalities were not apparent between the SX and TM patients. There was one operative death in the SX series and none among the TM patients. Total hospital mortality was 4% in the SX group and 2% in the TM group. In-hospital morbidity in the SX series (13/72-18%) was less than the TM group (14/42-33%), largely due to pleural entry and necessity for more frequent chest tube placement in TM patients. Electrode complications were low in both groups (3% in-hospital and 3% late; total 6/114, or 5%). Morbidity and mortality of these approaches to direct myocardial pacing remain noticeably higher than reported results of some transvenous series. Excellent electrode stability can be attained using the screw-on electrode, however, and the SX approach offers lower hospital morbidity than the TM method.

Adolescent↗
PubMed1981

Coronary flow and regional function before and after supraarterial myotomy for myocardial bridging.

Myocardial bridges have been associated with clinical and metabolic evidence of ischemia, although the mechanism for this is unclear. We measured coronary blood flow and segmental function at different heart rates prior to and after release of a myocardial bridge involving the left anterior descending coronary artery in a patient with angina. Before lysis of the bridge, atrial pacing was associated with a decreased systolic flow/total flow, increased duration of systole, a lag in diastolic flow, and functional deterioration. After release of the bridge, pacing was associated with increased systolic flow/total flow and systolic interval, no diastolic flow lag, and no functional deterioration. These data imply that before bridge division, systolic flow and the initiation of diastolic flow were impeded. Functional abnormalities resulting from the flow discrepancies at heart rates of 120 to 150 beats per minute may have accounted for this patient's symptoms.

Adult↗
PubMed1980

Paroxysmal hypotension associated with sympathetic withdrawal. A new disorder of autonomic vasomotor regulation.

We evaluated a patient who had transient episodes of hypotension with clinical and laboratory features apparently distinct from previously recognized disorders of vasomotor regulation. In between his abrupt attacks of hypotension, the patient is asymptomatic and demonstrates normal autonomic modulation of heart rate and blood pressure in response to changes in body position, Valsalva maneuver, cold, and exercise. During periods of hypotension, his plasma norepinephrine falls markedly and he has blunted or absent responses to stimuli that normally have a pressor effect due to sympathetic efferent discharge. Mechanical or known hormonal disorders that produce episodic hypotension have been excluded by extensive testing. We suggest two possible causes for our patient's paroxysmal sympathetic withdrawal: first, a centrally mediated inhibition of sympathetic discharge to peripheral resistance and capacitance vessels, but with no afferent stimulus reflexly producing sympathetic withdrawal readily evident; or second, an episodic release of an unknown endogenous compound with inhibitory effects upon central or preganglionic sympathetic neurons or upon postganglionic sympathetic neurons by a presynaptic inhibition of norepinephrine release.

Atropine↗
PubMed1979

Ventricular fibrillation in the Wolff-Parkinson-White syndrome.

To examine the risk of ventricular fibrillation in patients with the Wolff-Parkinson-White syndrome, we compared patients who had this syndrome and a history of ventricular fibrillation related to preexcitation with patients who had the syndrome without this history. Ventricular fibrillation occurred during atrial fibrillation, with rapid conduction over the accessory pathway, and these patients had a higher prevalence of both reciprocating tachycardia and atrial fibrillation (14 of 25 vs. 18 of 73, P = 0.004) and multiple accessory pathways (five of 25 vs. four of 73, P = 0.012). The shortest preexcitation R-R interval during atrial fibrillation was less in the group with ventricular fibrillation (mean shortest R-R, 180 vs. 240 milliseconds, P less than 0.0001) as was the average R-R interval (mean average R-R, 269 vs 340 milliseconds, P less than 0.0001). Patients with Wolff-Parkinson-White syndrome who are most susceptible to ventricular fibrillation have a history of atrial fibrillation and reciprocating tachycardia, demonstrate rapid conduction over an accessory pathway during atrial fibrillation and have multiple accessory pathways.

Adolescent↗
PubMed1977

Effects of procainamide and quinidine sulfate in the Wolff-Parkinson-White syndrome.

Thirty-three patients with Wolff-Parkinson-White syndrome were studied electrophysiologically before and after administration of intravenous procainamide and oral quinidine sulfate. Procainamide prolonged the shortest R-R (SRR) interval between two consecutive pre-excited beats during atrial fibrillation 20-70 msec in 15 of 21 patients with no change observed in 6 of 21 patients. Quinidine sulfate prolonged the SRR 20-170 msec in all 16. In 14 of 18 patients where procainamide and quinidine were comparable, quinidine prolonged the SRR 30-100 msec more than procainamide.

Atrial Fibrillation↗
PubMed1977

Digitalis in the pre-excitation syndrome. Analysis during atrial fibrillation.

The effect of digitalis in 21 patients with Wolff-Parkinson-White syndrome was anlayzed with respect to the ventricular response during atrial fibrillation and antegrade and retrograde refractory periods of accessory pathways. Digitalis shortened the cycle length of the most rapid ventricular response (shortest R-R) (i.e., increased the ventricle response) in 6/21 patients, increased the cycle length in 7/21 patients, had no effect on the cycle length in 5/21, and could not be determined in 3/21. Digitalis could be directly related to the onset of ventricle fibrillation resulting from atrial fibrillation in 9/21 patients. Each of these patients had shortest R-R intervals (220 msec or less) during atrial fibrillation in the control data. The results of this study indicate that no a priori prediction about the effect of digitalis on the antegrade conduction of accessory pathways can be made. By elective induction of atrial fibrillation it is possible to separate WPW patients into groups at high and low risk for developing ventricular fibrillation with the administration of digitalis.

Adolescent↗
PubMedDate not supplied

Cardiac ejection fraction: phantom study comparing cine MR imaging, radionuclide blood pool imaging, and ventriculography.

The accuracy and reproducibility of cardiac ejection fraction (EF) measurements based on cine magnetic resonance (MR) imaging, radionuclide multigated acquisition (MUGA) blood pool imaging, and angiographic ventriculography were evaluated by comparing them with a volumetrically determined standard. A biventricular, compliant, fluid-filled heart phantom was developed to mimic normal cardiac anatomy and physiology. Ventricular EFs were measured with cine MR imaging by summation of nine contiguous 10-mm-thick sections in short and long axis, with single-plane ventriculography, and with MUGA. Three measurements were performed with each modality for each of three EFs. Ventriculography was least accurate, with average relative errors ranging from 7.9% for the largest EF to 60.1% for the smallest. Cine MR was most accurate, with average relative errors ranging from 4.4% to 8.5%. MUGA EF measurements showed good correlation, with average relative errors ranging from 7.1% to 22.4%. Comparison of the error variances for the three modalities with the F test revealed that MR and MUGA EF measurements were significantly more accurate than those based on ventriculography (P less than .01). No significant difference was demonstrated between the accuracy of short- and long-axis cine MR acquisitions.

Gated Blood-Pool Imaging↗
PubMedDate not supplied

Balloon aortic valvuloplasty.

Balloon aortic valvuloplasty is a percutaneous, therapeutic option for patients with severe aortic stenosis, yet the effectiveness of this procedure is dependent on the morphology of the stenotic aortic valve and the respective mechanism of dilation. In younger patients with congenital aortic stenosis, acute and intermediate-term results are good. However, in adult patients, in whom degenerative aortic stenosis is the most common cause, the acute clinical and hemodynamic benefits of balloon aortic valvuloplasty are not lasting, as restenosis occurs in most patients within 6 months. Sympatomatic relief for adults undergoing balloon aortic valvuloplasty is only apparent in patients with normal left ventricular function, who generally are also candidates for aortic valve replacement. Furthermore, the long-term survival for adults after balloon aortic valvuloplasty is similar to the natural history of untreated severe aortic stenosis. In this article, the mechanism of balloon aortic valvuloplasty, as well as its clinical and hemodynamic effects, are reviewed in the context of the different morphological types of aortic stenosis. In addition, two large registries of adult patients treated with balloon aortic valvuloplasty provide important information regarding the acute and long-term results of this procedure and are reviewed.

Adult↗