6 results on '"Smith, M.-L."'
Search Results
2. Selective parasympathetic denervation following posteroseptal ablation for either atrioventricular nodal reentrant tachycardia or accessory pathways.
- Author
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Hamdan, Mohamed H., Page, Richard L., Hamdan, M H, Page, R L, Wasmund, S L, Sheehan, C J, Zagrodzky, J D, Ramaswamy, K, Joglar, J A, Adamson, M M, Barron, B A, and Smith, M L
- Subjects
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VENTRICULAR tachycardia , *CATHETER ablation , *NORADRENALINE , *ADRENALINE - Abstract
Baroreflex gain and coronary sinus norepinephrine and epinephrine levels were measured before and immediately after radiofrequency ablation in the posteroseptal region in 9 patients with atrioventricular nodal reentrant tachycardia or posteroseptal accessory pathways. Arterial baroreflex gain was significantly reduced after radiofrequency ablation (p = 0.046), whereas coronary sinus epinephrine and norepinephrine levels did not change significantly compared with preablation levels. [ABSTRACT FROM AUTHOR]
- Published
- 2000
- Full Text
- View/download PDF
3. Subnormal parasympathetic activity after cardiac transplantation.
- Author
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Smith ML, Ellenbogen KA, Eckberg DL, Sheehan HM, and Thames MD
- Subjects
- Cohort Studies, Heart innervation, Heart Failure surgery, Humans, Longitudinal Studies, Male, Middle Aged, Prospective Studies, Regression Analysis, Atrial Function physiology, Electrocardiography, Heart Rate physiology, Heart Transplantation physiology, Parasympathetic Nervous System physiopathology
- Abstract
Heart period variability (standard deviation of 120 consecutive RR or PP intervals) was used to assess baseline parasympathetic activity in 18 patients with congestive heart failure before and after orthotopic cardiac transplantation, and was compared to that of 16 age-matched control subjects. Mean heart period variability (+/- standard error of the mean) was significantly greater (p less than 0.05) in control subjects (58 +/- 5 ms) than in the patients at any time before or after transplantation. Heart period variability of innervated recipient atria did not change significantly early (1 to 4 weeks) after transplantation (16 +/- 2 to 24 +/- 5 ms; p = 0.11), but increased significantly between weeks 15 and 37 after transplantation (30 +/- 5 ms, p less than 0.002 versus before transplantation). A stepwise regression model (R2 = 0.35; p = 0.01) showed that heart period variability was directly related to time after transplantation and inversely related to systolic arterial pressure after transplantation and degree of rejection. Heart period variability of the denervated donor atria did not change from early to late periods after transplantation, suggesting that vagal reinnervation of the donor heart had not occurred. These data indicate that baseline parasympathetic activity does not increase significantly during the first month after transplantation but increases significantly between months 3 and 6.
- Published
- 1990
- Full Text
- View/download PDF
4. Changes in regional adrenergic tone during sustained ventricular tachycardia associated with coronary artery disease or idiopathic dilated cardiomyopathy.
- Author
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Ellenbogen KA, Smith ML, Thames MD, and Mohanty PK
- Subjects
- Forearm blood supply, Humans, Middle Aged, Phentolamine, Plethysmography, Receptors, Adrenergic, alpha physiology, Tachycardia physiopathology, Cardiomyopathy, Dilated complications, Coronary Disease complications, Sympathetic Nervous System physiology, Tachycardia etiology, Vascular Resistance physiology, Vasoconstriction physiology
- Abstract
The hemodynamic tolerance of an episode of ventricular tachycardia (VT) can vary widely from no decrease in systolic blood pressure to severe hypotension. Little is known about the factors responsible for these different responses in man. Previous animal studies have suggested an important role for vasoconstriction mediated by the alpha-adrenergic nervous system. To determine the magnitude and time course of changes in alpha-adrenergic tone during symptomatic sustained monomorphic VT, VT cycle length, mean and phasic arterial pressure, forearm blood flow (by venous occlusion plethysmography) and forearm vascular resistance were measured in 15 patients. Nine of these patients were studied before and after regional intraarterial alpha blockade with phentolamine. After the induction of VT (350 +/- 68 ms), mean forearm blood flow decreased from 3.2 +/- 1.1 to 2.2 +/- 0.8 ml/min/100 ml (p = 0.0002) and the forearm vascular resistance increased from 32 +/- 14 to 40 +/- 14 units (p = 0.01). There were no significant differences for forearm vascular resistance during the first and last 30 seconds of VT (41.3 +/- 14 vs 37 +/- 13 units). After the infusion of intraarterial phentolamine, there were no significant changes in the VT cycle length or mean arterial pressure, but the forearm vascular resistance increase during VT was blunted by 60 to 70%. Most patients with symptomatic VT demonstrate sympathetic vasoconstriction and these changes are maximal during the first 30 seconds of VT. This sympathoexcitatory response is due largely to stimulation of alpha-adrenoreceptors and may be mediated by arterial baroreflexes.
- Published
- 1990
- Full Text
- View/download PDF
5. Increased vagal cardiac nerve traffic prolongs ventricular refractoriness in patients undergoing electrophysiology testing.
- Author
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Ellenbogen KA, Smith ML, and Eckberg DL
- Subjects
- Cardiac Pacing, Artificial, Electrophysiology, Humans, Male, Middle Aged, Phenylephrine, Physical Stimulation, Reflex physiology, Stimulation, Chemical, Suction, Carotid Sinus physiology, Heart innervation, Heart Conduction System physiology, Vagus Nerve physiology
- Abstract
Stimulation of the vagus nerve in animals causes prolongation of sinus cycle length, atrioventricular nodal conduction and ventricular refractoriness. Vagal stimulation appears to have a protective effect in animal models of sudden death. The electrophysiologic effects of enhanced vagal activity on right ventricular (RV) refractoriness in man have not been studied previously. The comparative effects of enhanced vagal tone (neck suction to -60 mm Hg) on sinus cycle length and RV refractoriness were assessed in 26 patients. The electrophysiologic effects of vagal activation by stimulation of carotid baroreceptors with neck suction were compared to the effect of carotid and aortic baroreceptor stimulation with phenylephrine infusion in 12 patients. During neck suction, mean sinus cycle length (819 +/- 32 ms) was prolonged by 146 +/- 20 ms (p less than 0.0001). The mean RV effective refractory period (ERP) and functional refractory period (FRP) were prolonged by 4 +/- 1 ms and 5 +/- 1 ms (p = 0.0001 and 0.0002, respectively). The mean change in RV ERP and FRP correlated with the peak change in sinus cycle length during neck suction (r = 0.46 and r = 0.58, respectively). During intravenous phenylephrine infusion, the mean change in RV ERP and FRP was 5 +/- 2 ms (p less than 0.04) and 10 +/- 3 ms (p less than 0.01), respectively. These results show that reflex vagal stimulation with neck suction or phenylephrine infusion causes a small but significant prolongation in RV refractoriness. These findings imply that the potential benefits of enhanced vagal tone in preventing sudden death may be indirectly mediated by changes in ventricular refractoriness.
- Published
- 1990
- Full Text
- View/download PDF
6. Percutaneous transluminal angioplasty in patients with prior myocardial revascularization surgery.
- Author
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Pinkerton CA, Slack JD, Orr CM, Vantassel JW, and Smith ML
- Subjects
- Emergencies, Follow-Up Studies, Humans, Recurrence, Risk Factors, Time Factors, Angioplasty, Balloon, Coronary Disease therapy, Coronary Vessels, Graft Occlusion, Vascular therapy, Myocardial Revascularization
- Abstract
Direct myocardial revascularization surgery using either the saphenous vein or internal mammary artery has become the definitive surgical treatment for coronary artery occlusive disease. Certain patients who have undergone these procedures, however, have recurrent myocardial ischemia due to progression of disease in unbypassed vessels, to obstruction in the arteries distal to the insertion of the bypass conduit, or to disease of the conduit itself. Balloon angioplasty may be used to relieve myocardial ischemia in these situations; however, initial studies suggested a low primary success rate coupled with excessive mortality and morbidity. Improvements in patient selection, equipment and technical expertise now allow angioplasty to be performed in this patient population with results comparable to that in the general coronary angioplasty population. Of the 3,016 angioplasty procedures performed between September 1980 and June 1987, 236 patients had previously undergone revascularization surgery. The primary success rate was 93% (390 of 419 stenoses successfully dilated). Overall, clinical restenosis was observed in 39%, including a 43% restenosis rate in patients undergoing only saphenous vein graft angioplasty. This did not differ appreciably from the restenosis rate in postbypass patients undergoing angioplasty of only native vessels (37%) or internal mammary arteries (42%). Emergency revascularization surgery was required in 7 of 236 patients (3%), each of whom had myocardial infarction. One of 236 patients (0.4%) died. Thus, angioplasty may be used to relieve recurrent myocardial ischemia in patients with prior direct myocardial revascularization procedures with a high initial success rate and acceptable risk. Early (less than 6 months) restenosis is not infrequent and remains the largest obstacle to a satisfactory clinical outcome.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1988
- Full Text
- View/download PDF
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