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Biomedical subjects

C B Porter

Publications and source records attributed to C B Porter.

At least 19 recordsLinked to original sources
PubMed1996

Secular trends in cardiac transplant recipient and donor management in the United States, 1990 to 1994. A multi-institutional study. Cardiac Transplant Research Database Group.

BACKGROUND: The growth of the US cardiac transplant waiting list has outpaced the increase in donors, resulting in a widening gap between the number of waiting recipients and available donors. These trends have generated concern that longer waiting times may result in more patients deteriorating to urgent status and that transplanting only patients who are in an advanced state of decompensation will reduce posttransplant survival. Furthermore, the shortage of donors may result in extending the guidelines for donor acceptability to a degree that increases graft failure and posttransplant mortality. We measured these secular trends in the Cardiac Transplant Research Database to provide current data on time-dependent changes in US cardiac transplant practice and survival. METHODS AND RESULTS: At the time of this analysis, the Cardiac Transplant Research Database included all 2749 patients transplanted from January 1, 1990, to June 30, 1994, in the 25 participating transplant centers. During this 4.5-year period, the median waiting time for recipients who received a transplant increased from 2.7 to 3.5 months (P < .0001), and the proportion of recipients whose status was urgent at transplantation increased from 41% to 60% (P < .0001). Donor ischemic time increased from 150 to 166 minutes (P < .0001), and the proportion of donors requiring pressor support increased from 68% to 85% (P < .0001). Despite these changes in practice, the 1-year survival rate remained constant at 84% during this 4.5-year interval. There was no significant difference in 1-year survival rate between urgent status patients (83%) and nonurgent status patients (85%) (P = .08). CONCLUSIONS: The widening gap between the number of waiting recipients and the number of donors has resulted in a continuing trend toward transplanting urgent status recipients and to a liberalization of donor acceptance criteria. Despite these changes, posttransplant survival has remained constant.

Adult↗
PubMed1995

Diagnostic use of adenosine in two pediatric patients.

We describe the successful diagnostic use of adenosine in two pediatric patients. In the first case, adenosine infusion enabled exclusion of accessory pathway conduction in a patient who had previous evidence of Wolff-Parkinson-White syndrome. In the second case, adenosine infusion aided in the diagnosis of a nonreciprocating reentrant atrial tachycardia in a postoperative Fontan patient. The transient atrioventricular nodal blocking effect of adenosine added diagnostic certainty which was not apparent from the surface 12-lead electrocardiograms or rhythm recording in both patients. As the therapeutic use of adenosine for reciprocating supraventricular tachycardia in children becomes more popular, clinicians should also recognize the situations in which its use may facilitate diagnosis of other supraventricular rhythms.

Adenosine↗
PubMed1993

Sex-related differences in patients undergoing direct angioplasty for acute myocardial infarction.

Important sex-related differences have been recognized in several coronary artery disease presentation and treatment subsets. Little data exist describing the relative findings and outcome in women versus men who received direct percutaneous transluminal coronary angioplasty for acute myocardial infarction. We studied 670 such patients of whom 464 (69%) were men and 206 were women. The women were significantly older (67 +/- 11 years vs 61 +/- 11, p < 0.001) but had undergone less prior coronary artery bypass graft surgery (6% vs 12%, p = 0.02), whereas prior myocardial infarction (17% women vs 22% men) and coronary artery disease distribution were not significantly different. Forty-one percent of women and 43% of men had single-vessel disease (p = NS). Both women and men had 1.5 lesions/patient dilated acutely, with similar success rates (95% women, 91% men; p = 0.08). Mean ejection fractions were similar (48% in both groups), and a similar percentage in each group had an ejection fraction < 30% (10% women vs 13% men). Over a mean follow-up period of 86 weeks, the need for repeat catheterization was frequent and was similar in both groups (44% women, 47% men; p = NS), whereas documented restenosis was less common in women (20% vs 28% of patients, p < 0.05). The need for coronary artery bypass grafting was similar (15% women, 17% men; p = NS), as was the need for repeat percutaneous transluminal coronary angioplasty in the infarct vessel (14% women, 18% men; p = NS) and overall mortality (7% women, 9% men; p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Exercise echocardiography after coronary artery bypass grafting.

Exercise echocardiography was used to assess the adequacy of regional myocardial perfusion in 125 patients who had undergone coronary artery bypass grafting. There were 108 men and 17 women (mean age 65 years) evaluated from 6 weeks to 16 years (mean 7 years) after surgery. Resting parasternal long- and short-axis and apical 4- and 2-chamber echocardiograms were recorded, digitized and stored. Maximal, symptom-limited upright treadmill exercise was then performed with continuous electrocardiographic monitoring. Repeat echocardiographic imaging and digitization were repeated within 1 minute of exercise termination. Resting and postexercise digitized echocardiograms were compared. A normal regional wall motion response to exercise consisted of improved segmental contraction and was used to predict uncompromised regional vascular supply. Unimproved or worsened segmental contraction after exercise was abnormal and was used as a predictor of regional vascular insufficiency. All patients underwent cardiac catheterization within 1 month after exercise testing. Regional coronary insufficiency was considered to exist when a segment's major vascular conduit exhibited greater than or equal to 50% luminal diameter reduction. Compared with the simultaneously acquired stress electrocardiogram, exercise echocardiography had superior sensitivity (98 vs 41%), specificity (92 vs 67%), positive predictive value (99 vs 91%), and negative predictive value (86 vs 12%) (p less than 0.001, 0.1, 0.01 and less than 0.001, respectively). In addition, exercise echocardiography correlated closely with the extent and regional distribution of compromised vascular supply. Exercise echocardiography is a highly sensitive, specific and accurate screening test for abnormal global and regional myocardial vascular supply in patients who have undergone coronary artery bypass grafting.

Aged↗
PubMed1991

Antitachycardia pacemaker treatment of postoperative arrhythmias in pediatric patients.

An automatic antitachycardia pulse generator (Intertach 262-12) was implanted in each of six pediatric patients (mean age, 10 years) with drug-resistant and persistent postoperative supraventricular arrhythmias. Four had bradycardia-tachycardia syndrome, two after a Mustard procedure for transposition of the great arteries, one after a Senning procedure for the same anomaly, and one after a Fontan procedure for univentricular heart with transposition of the great arteries. Of the two remaining patients, one had atrial flutter after a modified Fontan procedure for univentricular heart and one had intra-atrial reentry tachycardia after a modified Fontan procedure for double-outlet right ventricle with pulmonary stenosis. During a mean follow-up interval of 31 months after implantation, pacemakers were activated on multiple occasions and functioned appropriately in all six patients. Complications necessitated six invasive interventions in three patients: erosion or infection of the system, adaptor fracture, and connector block fracture on one occasion each and lead dislodgment on three occasions. Four of the six patients continued to take drugs at the end of this study; however, all patients had their drug therapy reduced and one was taking digoxin only. The number of hospital admissions decreased after implantation. Despite a number of technical challenges, this newer multiprogrammable antitachycardia pacemaker appears to be a valuable addition to the treatment of refractory postoperative supraventricular tachyarrhythmias in pediatric patients.

Adolescent↗
PubMed1989

The effects of hypoxemia on myocardial blood flow during exercise.

We evaluated the adequacy of regional and transmural blood flow during exercise and rapid pacing after 1 wk of hypoxemia. Seven mature mongrel dogs were made hypoxemic (mean O2 saturation = 72.4%) by anastomosis of left pulmonary artery to left atrial appendage. Catheters were placed in the left atrium, right atrium, pulmonary artery, and aorta. Atrial and ventricular pacing wires were placed. An aortic flow probe was placed to measure cardiac output. Ten nonshunted dogs, similarly instrumented, served as controls. Recovery time was approximately 1 wk. Cardiac output, mean aortic pressure, and oxygen saturation were measured at rest, with ventricular pacing, atrial pacing, and with treadmill exercise. Ventricular and atrial pace and exercise were at a heart rate of 200. Right ventricular free wall, left ventricular free wall, and septal blood flow were measured with radionuclide-labeled microspheres. Cardiac output, left atrial blood pressure, and aortic blood pressure were similar between the two groups of dogs in all testing states. Myocardial blood flow was significantly higher in the right and left ventricular free wall in the hypoxemic animals during resting and exercise testing states. Myocardial oxygen delivery was similar between the two groups of animals. Pacing resulted in an increase in myocardial blood flow in the control animals but not the hypoxemic animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Results of the modified Fontan operation in adults.

The results of the modified Fontan procedure were examined in 77 patients 18 years of age and older who underwent operation at this institution between October 1973 and December 1986. This series represents 16% of the patients undergoing the modified Fontan operation during that period. Of the 77 patients (46 men and 31 women), 29 had tricuspid atresia, 30 had double-inlet ventricle and 18 had other complex lesions. There were 5 (6%) hospital deaths, compared with 67 (17%) for patients of all ages undergoing the Fontan operation during the same period. Patient age 18 years and older was not a significant risk factor. There were 8 late deaths. Detailed follow-up data were available on 61 (95%) survivors from 5 months to 12 years (mean 4 years) postoperatively. Fifty-seven (93%) of the patients were in New York Heart Association class I or II, 20 (33%) were taking no medication and 11 (18%) were taking digoxin alone. Seventeen (28%) patients complained of persistent ascites or edema. The study indicated that (1) the modified Fontan operation can be performed with low mortality in adults, (2) the long-term outcome is favorable and (3) persistent ascites or edema may be a problem in some patients.

Adolescent↗
PubMed1988

Cryosurgical modification of atrioventricular conduction for treatment of atrioventricular node reentrant tachycardia.

Cryosurgical modification of atrioventricular (AV) node conduction was performed in five patients with AV node reentrant tachycardia that used dual AV nodal pathways and was refractory to drug therapy. The procedure alleviated the tachycardia in all patients without the development of complete heart block and without any associated surgical morbidity or mortality. These results suggest that cryosurgical modification of AV node conduction is a promising and potentially curative method of treating AV node reentrant tachycardia.

Adolescent↗
PubMed1987

Plasma atrial peptide concentration during acute changes in cardiac filling pressure induced by a contrast agent.

Left ventricular end-diastolic pressure and the concentration of atrial peptides in plasma were measured before and after the administration of contrast material into the left ventricle of 12 patients during cardiac catheterization. A positive relationship between changes in left ventricular end-diastolic pressure and the circulating level of atrial peptides was found in all 12 patients. Increases in plasma atrial peptide levels were detected within less than one minute after injection of the contrast agent. We conclude that the release of atrial peptides in the human is modulated rapidly by changes in atrial pressure. The rapid release of peptides from the atria in response to an increase in atrial pressure, coupled with evidence that atrial peptides reduce cardiac filling pressure, is consistent with the possibility that the atrial peptides may serve as part of a negative feedback system that enables the heart to influence its own filling pressure.

Adult↗
PubMed1986

Clinical intracardiac electrophysiologic testing: technique, diagnostic indications, and therapeutic uses.

Clinical cardiac electrophysiologic testing has evolved rapidly since 1968, when the technique was first described. In an electrophysiologic study, electrode catheters are positioned within the heart to record electrical activity from the atrium, atrioventricular conduction tissue, and ventricle. Programmed stimulation is then performed, which involves pacing of the atrium or ventricle and introducing critically timed premature stimuli during sinus rhythm or paced rhythm. The use of programmed stimulation in conjunction with intracardiac recordings in electrophysiologic studies has facilitated the diagnosis of mechanisms of arrhythmias and the assessment of therapy. Electrophysiologic testing is useful in selected patients with sinus node dysfunction, conduction system disorders, supraventricular tachycardia, ventricular tachycardia, or ventricular fibrillation and in survivors of out-of-hospital cardiac arrest and patients with symptomatic but unsubstantiated rhythm disturbances. Therapeutic approaches that can be assessed by electrophysiologic testing include serial drug testing to determine the effectiveness of antiarrhythmic agents, antitachycardia pacing, the implantable defibrillator, transcatheter ablation, and electrophysiologically guided surgical procedures. In this review, we discuss the methods of electrophysiologic testing, its clinical applications in diagnosing the various cardiac rhythm disturbances, and its use in assessing various therapeutic modalities.

Anti-Arrhythmia Agents↗
PubMed1985

Surgical treatment of accessory atrioventricular pathways and symptomatic tachycardia in children and young adults.

Twenty-seven patients aged 21 years or younger (mean 15) with symptomatic tachycardia underwent operation for ablation of an accessory atrioventricular pathway. Six patients had associated Ebstein's malformation of the tricuspid valve. Supraventricular tachycardia had been present for a mean of 5 years. At electrophysiologic study, 4 patients were found to have 2 accessory pathways. Left ventricular free wall pathways were found in 14 patients, right ventricular free wall pathways in 10 and septal pathways in 6. Successful initial ablation of all the pathways was achieved in 26 of the 27 patients. No patient died perioperatively and none had persistent complete heart block. During a mean follow-up of 11 months, no patient had recurrence of an arrhythmia related to the accessory pathway. Thus, the surgical treatment of children and young adults with accessory atrioventricular pathways and symptomatic supraventricular tachycardia is safe and effective. For these patients, unless the tachycardia can be easily controlled with a minimal number of drugs and adverse effects, surgical ablation should be considered early in the clinical course.

Adolescent↗
PubMed1985

Improved myocardial oxygen utilization by diltiazem in patients.

Calcium entry blocking drugs produce different effects on systemic and coronary hemodynamics and myocardial oxygen extraction. To examine the effects on myocardial oxygen extraction, intravenous diltiazem (100 micrograms/kg bolus with a continuous 10 micrograms/kg/min infusion) was administered to 11 patients at rest and during controlled heart rates (100 +/- 5 and 120 +/- 5 bpm). At rest, diltiazem decreased mean arterial pressure from 109 +/- 13 to 99 +/- 14 mm Hg (p less than 0.01), increased heart rate from 64 + 12 to 74 +/- 14 bpm (p less than 0.01), and decreased coronary sinus resistance (1.02 +/- .41 to 0.87 +/- .40 U, p less than 0.05). Myocardial oxygen extraction was significantly reduced since coronary sinus oxygen content increased (6.0 +/- 0.9 to 7.8 +/- 1.2 ml/dl, p less than 0.01) and the arterial-coronary sinus oxygen difference decreased (12.0 +/- 1.7 to 10.6 +/- 1.6 ml/dl, p less than 0.01). Similar changes occurred with heart rate held constant. There were no significant changes in absolute coronary sinus blood flow, calculated myocardial oxygen consumption, or left ventricular dP/dt. Diltiazem decreases mean arterial pressure while reducing both myocardial oxygen extraction and coronary arterial resistance, suggesting that a principal mechanism of a beneficial effect upon the coronary circulation appears to be an improvement in myocardial oxygen extraction relative to myocardial oxygen demand.

Adult↗
PubMed1985

Cardiac arrhythmias in patients with surgical repair of Ebstein's anomaly.

Preoperative, perioperative and postoperative arrhythmias in 52 consecutive patients who underwent operation for Ebstein's anomaly were reviewed. There were 25 male and 27 female patients (mean age 18 years, range 11 months to 64 years). Thirty-four patients had one or more documented arrhythmias preoperatively (18 had paroxysmal supraventricular tachycardia, 10 had paroxysmal atrial fibrillation or flutter, 13 had ventricular arrhythmia and 3 had high grade atrioventricular block). Seven patients without documented arrhythmias had a history typical of tachyarrhythmias. During the perioperative and early postoperative periods, 14 patients had atrial tachyarrhythmias and 8 had ventricular tachycardia or ventricular fibrillation. There were seven deaths between day 1 and 27 months after operation. Five of these deaths were sudden (all in male patients, aged 12 to 34 years), and four of the patients had had perioperative ventricular tachycardia or ventricular fibrillation. One patient was taking one antiarrhythmic agent and another patient was taking two at the time of sudden death. Of the 18 patients with paroxysmal supraventricular tachycardia and 9 patients with paroxysmal atrial fibrillation or flutter preoperatively who were followed up for a mean of 40 and 36 months, respectively, 22 and 33% continued to have symptomatic tachycardia. Of the 11 patients (mean age 9 years) without preoperative documentation or symptoms of arrhythmia, follow-up data were obtained (range 1 to 144 months, mean 31) in 9 patients. None died suddenly or developed symptomatic arrhythmia.

Adolescent↗
PubMed1985

Results of the modified Fontan operation for congenital heart lesions in patients without preoperative sinus rhythm.

Preoperative sinus rhythm has been a criterion for the Fontan operation. However, of 297 patients who underwent the Fontan operation between October 1973 and February 1984, 12 (4%) did not have sinus rhythm. The age at operation ranged from 4 to 34 years (median 15). Nine patients had a univentricular heart, two had tricuspid atresia and one had a complex form of transposition. In all 12 patients, 3 to 8 of the 10 proposed criteria for operability were not met. An atrioventricular (AV) conduction abnormality was present in seven patients, six with complete AV block and one with AV dissociation. The patient with complex transposition had complete AV block and atrial fibrillation. Postoperatively, all seven patients continued to have an AV conduction abnormality, and those with complete AV block had a permanent pacemaker implanted. Six of the 12 study patients had atrial flutter or fibrillation refractory to antiarrhythmic medications. Postoperatively, four of the six patients had sinus rhythm. Two of the six patients had complete AV block (including the patient with complex transposition) and both had a permanent pacemaker implanted. Three of the 12 patients died (mortality rate 25%). The nine survivors were followed up for 6 to 55 months; no late deaths occurred. All had marked clinical improvement. This study demonstrates that 1) complete AV block is not a contraindication to the Fontan operation, 2) some patients may not require AV synchrony postoperatively for survival, and 3) postoperative atrial flutter or fibrillation may cease or be easier to control after the Fontan operation.

Adolescent↗
PubMed1985

Regional coronary vasoconstriction after combined beta-adrenergic and calcium channel blockade in patients with coronary artery disease.

The beta-adrenergic and calcium channel blocking drugs, which individually and combined have proven efficacious in the treatment of angina pectoris, appear to have opposing effects on coronary artery vasomotion. Previous studies have shown that beta-adrenergic blockade may potentiate and calcium channel blockade reverse coronary vasoconstriction during adrenergic cold stimulation in patients with coronary artery disease. To assess the coronary hemodynamic effects of combined drug therapy, thermodilution coronary sinus and great cardiac vein flow and mean arterial pressure were measured during serial cold pressor testing, both before and after 0.1 mg/kg of intravenous propranolol and again after the addition of 10 mg of sublingual nifedipine in 21 patients (9 without [group A1] and 12 with [group A2] greater than 50% narrowing of the left anterior descending coronary artery). In an additional 15 patients (6 patients without [group B1] and 9 with [group B2] left anterior descending artery stenosis), serial cold pressor testing was performed reversing the drug order. Despite significant increases in mean arterial pressure (p less than 0.01) during cold pressor testing, coronary sinus resistance responses after propranolol plus nifedipine were not statistically significant for any group. However, regional coronary resistance responses differed between patients with and without left anterior descending artery stenosis. In group A1, great cardiac vein resistance was unchanged after propranolol plus nifedipine. In group A2, great cardiac vein flow decreased significantly after propranolol plus nifedipine from 8 +/- 17 to -4 +/- 12% (p less than 0.01 versus control), and great cardiac vein resistance increased from 4 +/- 21 to 15 +/- 19% (p less than 0.01 versus control). A similar significant response was observed for groups B1 and B2. Regional coronary vasoconstriction during adrenergic stimulation after combined drug therapy was only observed in patients with significant left anterior descending artery stenosis. These data suggest that in some patients with severe coronary artery disease, combined beta-adrenergic and calcium channel blockade modified regional coronary responses to adrenergic stimulation with an inhomogeneous distribution of blood flow to potentially ischemic regions without affecting total coronary blood flow. These data also imply that an improvement in anginal symptoms after combined drug therapy may be due primarily to mechanisms that reduce myocardial oxygen demand rather than to improved myocardial oxygen supply.

Adrenergic beta-Antagonists↗
PubMed1984

Anterior pontic design: a logical progression.

The fixed partial denture with multiple pontics can be enhanced by the elimination of embrasures between pontics while basic adherence to established design concepts is maintained. Continuing clinical observations are indicated.

Denture Design↗