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 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have analyzed results in 54 consecutive patients with recurrent ventricular tachycardia and coronary artery disease in whom we used an aggressive surgical approach involving map-directed ventricular tachycardia ablation, scar excision and left ventricular remodeling, and coronary artery bypass grafting, as well as staged mitral valve replacement when necessary. We have previously shown age greater than 65 years to be an independent predictor of mortality and have excluded such patients from this series. Average age was 56 +/- 7 years. All patients had a previous myocardial infarction; 24% of the infarctions (13/54) were posterior in location. Symptoms included syncope or presyncope in 83% of the patients (45/54), angina in 54% (29/54), and congestive heart failure in 52% (28/54). Extensive coronary artery disease was found in 78% (42/54), and 89% (48/54) had serious compromise of left ventricular function (ejection fraction < 0.40; average ejection fraction, 0.28 +/- 0.12). Only 63% (34/54) appeared to have a resectable left ventricular aneurysm on the preoperative angiogram. Ablation techniques included endocardial excision in 82% (44/54), with the addition of cryoablation in 60% (32/54), and balloon electric shock ablation in 22% (12/54); coronary artery bypass grafting was performed in 85% (46/54). There were four hospital deaths (7%). The surgical cure rate (no inducible VT at postoperative electrophysiologic study was 72% (39/54). During follow-up (mean, 50 +/- 31 months) there have been six late deaths (1 sudden death, 1 stroke, 4 congestive heart failures with or without mitral regurgitation). Four patients with progressive congestive heart failure and serious mitral regurgitation have undergone repeat operation for mitral valve replacement.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Late results of operation for ventricular tachycardia. 141 72

Eight young men underwent an 8-month endurance exercise training program. Prior to and following the training program, the subjects' maximal oxygen uptake (VO2max), total blood volume (TBV) and plasma volume (PV), tolerance to lower body negative pressure (LBNP) assessed by the cumulative stress index (CSI) to presyncope, and their hemodynamic responses to 0 to -45 torr LBNP was determined. Hemodynamic measures included rebreathe carbon dioxide cardiac output (Qc), heart rate (HR), directly measured arterial blood pressures (ABP), and strain gauge determination of forearm blood flow (FBF) and leg volume changes (delta LgV). Calculated values of stroke volume (SV), forearm, vascular resistance (FVR), and peripheral vascular resistance (PVR) were made. Following training, each subject had an increased VO2max (mean = +27.4%, P < 0.001), TBV (mean = +15.8%, P < 0.02), and PV (mean = +16.5%, P < 0.02) and each subject had a decreased tolerance to LBNP (mean CSI = -24%, P < 0.001). Stepwise linear regression identified that the major factors to significantly predict the decreased CSI pre- to post-training were a reduced response of PVR to LBNP from -15 to -45 torr (Model R2 = 0.853), the delta TBV (model R2 = 0.981), and the greater post-training reduction in SBP to LBNP of 0 to -45 torr (model R2 = 1.0). These data suggest that physiologic adaptations associated with the increased VO2max and TBV resulting from a prolonged endurance exercise training program can alter the reflex control of vasomotion and cardiac output during LBNP and reduce the LBNP tolerance.
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PMID:Reduction in LBNP tolerance following prolonged endurance exercise training. 143 75

The haemodynamic response to lower body negative pressure (LBNP) was studied in 6 test subjects before (baseline), during, and after (recovery) ten days of 6 degrees head-down bedrest. The LBNP protocol consisted of a 35 min control period, application of a staircase differential pressure profile (15 min at -15 mmHg; 5 min at -30 mmHg; 15 min at -40 mmHg), and a 10 min post-stress observation period. Cardiac output was measured by a foreign gas rebreathing technique. Finger plethysmographic arterial blood pressure (BP), ECG, and heart rate (HR), lower limb crossectional area, and the electrical impedance of three body segments were recorded continuously. As expected, HDT caused a decrease in plasma volume and total body fluid volume. Resting CO at the end of HDT was 16% below the baseline level and similar to CO in the upright position before HDT. Stroke volume (SV) was also reduced, but there were no significant changes in control HR or BP. Absolute changes in CO and SV during LBNP were similar at baseline and during HDT, but the relative changes were larger during HDT. HR and vasoconstriction responses were enhanced, but presyncope occurred in two subjects. Reduced cardiac filling with decreased stroke volume at rest is the apparent primary cause of the altered LBNP response during HDT.
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PMID:Cardiovascular response to lower body negative pressure before, during, and after ten days head-down tilt bedrest. 150 93

We studied three groups of eight men each--high, mid, and low fit (peak O2 consumption 60.0 +/- 0.8, 48.9 +/- 1.0, and 35.7 +/- 0.9 ml.min-1.kg-1)--to determine the mechanism of orthostatic intolerance in endurance athletes. Tolerance was defined by progressive lower body negative pressure (LBNP) to presyncope. Maximal calf vascular conductance (Gmax) was measured. The carotid baroreflex was characterized using both stepwise R-wave-triggered and sustained (2 min) changes in neck chamber pressure. High-fit subjects tended to have lower LBNP tolerance than mid- and low-fit subjects but similar baroreflex responses. Subjects with poor LBNP tolerance had larger stroke volumes (SV) (120 +/- 6 vs. 103 +/- 3 ml) and greater decline in SV with LBNP to -40 mmHg (40 +/- 2 vs. 26 +/- 4%). Stepwise multiple linear regression analysis revealed that Gmax and steady-state gain of the carotid baroreflex contributed significantly toward explaining interindividual variations in LBNP tolerance. Thus endurance athletes may have decreased LBNP tolerance, but apparently not as a simple linear function of aerobic fitness. Orthostatic tolerance depends on complex interactions among functional characteristics that appear both related (Gmax and SV) and unrelated (baroreflex function) to fitness or exercise training.
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PMID:Physical fitness and cardiovascular regulation: mechanisms of orthostatic intolerance. 201 Mar 66

Thirty-three patients with ventricular tachycardia (VT) (3 or more beats, less than 30 seconds in duration, rate more than 100 per minute) on 24-hour Holter monitoring and no history of clinical arrhythmia (presyncope, syncope or sudden death) were studied using programmed electrical stimulation (PES). PES induced VT in 14 patients (42%), sustained VT in 7 (21%) and nonsustained VT in 7 (21%). Inducible VT was associated with underlying heart disease in 9 of 19 patients with coronary artery disease, 3 of 6 patients with idiopathic dilated cardiomyopathy and 2 of 4 patients with mitral valve prolapse. Patients without structural heart disease did not have inducible VT. Ejection fraction (EF) was not significantly different in patients with or without inducible VT. Twenty-three patients were discharged with drug therapy and 10 patients without therapy. At 23 +/- 16 months (mean +/- standard deviation) follow-up, 28 patients (85%) were alive, 4 (12%) had died from a cardiac cause (EF 49 +/- 17% vs 28 +/- 20%, p less than 0.03). Another patient died from cerebrovascular accident. Twenty-six patients (79%) were free of clinical arrhythmia and 7 patients (21%) had arrhythmic events (EF 49 +/- 18% vs 31 +/- 17%, p less than 0.04). Two of 8 patients with noninducible VT who were discharged without drug treatment had clinical arrhythmic events and neither of 2 patients with inducible VT discharged off drugs had such events.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Programmed electrical stimulation and long-term follow-up in asymptomatic, nonsustained ventricular tachycardia. 402 71

Emergencies that arise out of psychophysiologic responses are rarely life-threatening and can be managed readily by the alert dental office team. It is imperative, however, to use all available information during the emergency assessment. Inaccurate diagnosis and treatment as a result of confusion between presyncope and hyperventilation may result in an accelerated onset of the emergency episode. Rapid recognition of an impending alteration of consciousness should minimize the progression toward or reduce any period of unconsciousness. If unconsciousness occurs, basic life support and supine positioning with supplemental oxygen should be provided immediately. Finally, the dental team should be prepared to treat other life-threatening emergencies that might initially present as syncope, such as cardiac arrest, stroke, or anaphylactic reactions.
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PMID:Anxiety. Its manifestation and role in the dental patient. 755 87

Hemodynamic, cardiac, and hormonal responses to lower-body negative pressure (LBNP) were examined in 24 healthy men to test the hypothesis that responsiveness of reflex control of blood pressure during orthostatic challenge is associated with interactions between strength and aerobic power. Subjects underwent treadmill tests to determine peak oxygen uptake (VO2max) and isokinetic dynamometer tests to determine knee extensor strength. Based on predetermined criteria, subjects were classified into one of four fitness profiles of six subjects each, matched for age, height, and body mass: (a) low strength/average aerobic fitness, (b) low strength/high aerobic fitness, (c) high strength/average aerobic fitness, and (d) high strength/high aerobic fitness. Following 90 min of 0.11 rad (6 degrees) head-down tilt (HDT), each subject underwent graded LBNP to -6.7 kPa or presyncope, with maximal duration 15 min, while hemodynamic, cardiac, and hormonal responses were measured. All groups exhibited typical hemodynamic, hormonal, and fluid shift responses during LBNP, with no intergroup differences between high and low strength characteristics. Subjects with high aerobic power exhibited greater (P < 0.05) stroke volume and lower (P < 0.05) heart rate, vascular peripheral resistance, and mean arterial pressure during rest, HDT, and LBNP. Seven subjects, distributed among the four fitness profiles, became presyncopal. These subjects showed greatest reduction in mean arterial pressure during LBNP, had greater elevations in vasopressin, and lesser increases in heart rate and peripheral resistance. Neither VO2max nor leg strength were associated with fall in arterial pressure or with syncopal episodes. We conclude that interactions between aerobic and strength fitness characteristics do not influence responses to LBNP challenge.
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PMID:Hemodynamic and hormonal responses to lower body negative pressure in men with varying profiles of strength and aerobic power. 814 27

Hemodynamic and hormonal responses to lower body negative pressure (LBNP) after 12-h head-down tilt (HDT) were examined to investigate the mechanism of orthostatic intolerance following spaceflight. Ten young healthy male volunteers participated in the experiment. After 6 degrees HDT for 12 h, the tolerance to 1 h continuous -30 mm Hg LBNP was tested. Variables were measured before and after HDT, during LBNP, and 1 and 10 min after LBNP. Significant reduction in leg volume and plasma volume were observed at the end of 12-h HDT (500 ml and 5.5%, respectively). In the tolerant group, stroke volume index (SI) was decreased by 35% after 15 min LBNP, and carotid arterial blood flow (CBF), by 27% at the end of LBNP compared to the pre-LBNP value. Of the 10 subjects, 5 developed presyncope during LBNP; they exhibited remarkable reduction in SI, CBF, and heart rate, and increased secretion of ADH and adrenaline during or just prior to presyncope. This non-tolerant group tended to be hemo-concentrated from the start of the experiment. However, it will require a prospective study to determine if this variable is a reliable predictor of the outcome of the post-HDT LBNP test from data collected at the end of HDT.
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PMID:Hemodynamic and hormonal correlates with exposure to lower body negative pressure after 12 hours head-down tilt. 835 12

Atrial fibrillation is most the common sustained arrhythmia seen by the cardiologist. Therapy to prevent this arrhythmia is often prescribed so as to eliminate associated symptoms which include palpitations, fatigue, dizziness and presyncope, shortness of breath, congestive heart failure and emboli, especially those that result in a cerebrovascular accident. Pharmacologic therapy is the only effective therapy for preventing atrial fibrillation and the class 1 antiarrhythmic drugs remain the most frequently used agents. Although each of these agents has been reported to be effective for preventing atrial fibrillation, they are associated with frequent side effects, some of which are potentially serious, especially aggravation of arrhythmia. Prior to treatment the benefit vs risk of these drugs for each patient must be established.
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PMID:Class 1 antiarrhythmic agents for therapy of atrial fibrillation. 845 55

A retrospective analysis of patients with hypertrophic obstructive cardiomyopathy treated by left ventricular myotomy and myectomy from 1972 to 1994 is reported. There were 158 patients (81 male and 77 female) with a mean age of 50.2(+/-17.2) years (range 12 to 80 years). One hundred nine patients (69%) were 60 years of age or younger, and 49 patients (31%) were older than 60 years. The overall mean follow-up period was 6.1(+/-4.8) years (range 0.1 to 19.3 years) and was 94% complete with a cumulative total of 956 patient-years. Preoperative exertional dyspnea was present in 84%, chest pain in 70%, presyncope in 54%, syncope in 31%, and cardiac arrest in 5% of patients. Preoperative cardiac catheterization was done in 150 patients, with mitral regurgitation detected in 104 patients (67%). The average maximal provocable left ventricular outflow tract gradient was 118 (+/-46) mm Hg (range 25 to 250 mm Hg). The average preoperative echocardiographic gradient at rest was 64 mm Hg, 20 mm Hg in the early postoperative period and 10 mm Hg in the late postoperative period. The mean septal thickness was 2.2 (+/-0.6) cm, 1.9 (+/-0.7) cm in the early postoperative period (p < 0.05 vs preoperative) and 1.7 (+/- 0.5) cm in the late postoperative period (p < 0.05 vs preoperative). The overall 30-day operative mortality rate was 3.2% (5/158), and 0% for 109 patients 60 years of age or younger. Causes of death included myocardial infarction and left ventricular free wall rupture, myocardial failure from septal perforation, sepsis, cerebrovascular accident caused by thromboembolism, and delayed cardiac tamponade in one patient each. Concomitant coronary artery bypass grafting was performed in 22 patients (19.3% of patients > or = to 40 years of age) and mitral valve replacement in 5 patients (3.2%). One hundred nine patients (69%) are alive, 10 patients (6.3%) were lost to follow-up, and 39 patients died (24.7%), including operative deaths). Actuarial survivals at 1, 5, 10, and 15 years were 92.4% +/- 2.2%, 85.4% +/- 3.1%, 71.5 +/- 4.6%, and 46% +/- 9%, respectively. The overall linearized death rate for discharged patients was 1.9%/pt-yr, and for cardiac related deaths it was 1.7%/pt-yr. Thirty-nine (36%) of the 109 survivors received beta-adrenergic blockers, and 30 (28%) received calcium channel blockers. Ninety-four patients had improvement in New York Heart Association functional class, 10 had improvement in symptoms but not in functional class, and 5 had no improvement in functional class or symptoms. Neither preoperative hemodynamic values nor routine echocardiographic measurements significantly correlated with quality of postoperative results. Left ventricular myotomy and myectomy is a safe and reproducibly effective operative treatment for medically refractory hypertrophic obstructive cardiomyopathy, especially for patients 60 years of age or younger. Improvement in functional class and symptoms can be expected in nearly all patients 60 years of age or younger. Improvement in functional class and symptoms can be expected in nearly all patients. The results of myotomy and myectomy serve as a standard for comparison with other interventions for medically refractory cardiomyopathy.
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PMID:Long-term results of left ventricular myotomy and myectomy for obstructive hypertrophic cardiomyopathy. 860 73


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