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D J Patton

Publications and source records attributed to D J Patton.

5 recordsLinked to original sources
PubMed1996

Baroreflex gain: characterization using autoregressive moving average analysis.

To study heart rate baroreflex gain, autoregressive moving average (ARMA) analysis, a multivariate method that allows evaluation of the dynamic ("beat-to-beat") interactions between changes in biological signals, was used to evaluate the relationships between R-R interval and arterial blood pressure (BP) during random-interval breathing. Parameters obtained by ARMA analysis of spontaneous fluctuations in BP and R-R interval in 17 volunteers were used to model the response of R-R interval to a transient 1-mmHg increase in BP; the resulting impulse-response and step-response curves were compared with baroreflex gain measured using bolus injections of phenylephrine (PE) and sodium nitroprusside (SNP). Impulse-response curves for the systolic BP-R-R relationship showed an early (0-1 s) sharp maximum of 5.5 +/- 4.2 ms/mmHg, which was smaller in magnitude but linearly correlated with baroreflex gain derived from SNP (14.5 +/- 9.7 ms/mmHg; r = 0.80, P < 0.002) and PE (31.6 +/- 26.7 ms/mmHg; r = 0.53, P < 0.05) injections. A similar relationship was also found between the one-beat ARMA step response and SNP injection (r = 0.70, P = 0.01). The integrated step response of the BP-R-R relationship over 6 s was 6.4 +/- 4.1 ms/mmHg, with no correlation to baroreflex gain determined by SNP (r = 0.33, P = 0.20) or PE (r = -0.15, P = 0.57). In conclusion, quantification of baroreflex gain consistent with other techniques may be achieved by ARMA analysis without perturbing mean BP. Correlation of baroreflex gain obtained by bolus injection to early measures of baroreflex gain obtained from the ARMA maximum impulse and early step responses, but not the late step response, suggests that the ARMA method may provide additional information regarding the frequency dependent effects of BP on R-R-interval.

Adolescent↗
PubMed1994

Safety and durability of redo carotid endarterectomy for recurrent carotid artery stenosis.

We retrospectively reviewed the records of patients who underwent redo carotid endarterectomies during a 5-year period. Patients were followed by duplex ultrasound to assess late patency of the carotid artery. Reoperations for recurrent carotid stenosis were performed in 46 of 973 patients who had carotid endarterectomies (5%). Indications for surgery were hemispheric transient ischemic attacks (TIA) in 33 (72%) and asymptomatic greater than 80% stenosis in 13 (28%). Pathologic findings revealed that the cause of recurrence was myointimal hyperplasia in 11 patients (24%), with a mean recurrence interval of 12.8 postoperative months, and atherosclerosis in 35 (76%), with a mean recurrence interval of 84 postoperative months (P = 0.0002). Redo endarterectomy with patch angioplasty was used for reconstruction in 32 cases (70%), patch angioplasty alone in 11 (24%), and endarterectomy with primary closure in 3. There were 3 perioperative strokes (7%). Late follow-up (mean 30.9 months) revealed no strokes and 1 TIA. Of 40 patients, 34 (85%) were alive and stroke free. Although six late deaths occurred, none were stroke related. One patient (2%) had late significant second recurrent carotid stenosis. Redo carotid endarterectomy for symptomatic patients and asymptomatic high-grade stenosis is safe and durable.

Adult↗
PubMed1994

Postnatal maturation of baroreflex heart rate control in neonatal swine.

OBJECTIVE: Despite extensive knowledge about basic baroreceptor function, there continues to be controversy as to whether there is postnatal maturation of the cardiovascular baroreflex. DESIGN/ANIMALS: Acutely studied postnatal developmental changes in baroreflex sensitivity with a neonatal porcine model in 28 chloralose-anesthetized piglets from birth to six weeks of age. INTERVENTIONS: Steady-state heart rate versus blood pressure response curves were generated by altering blood pressure with increasing doses of phenylephrine or nitroprusside. Data were fitted to the Hill equation for sigmoidal curves, and the maximum heart rate, maximum slope (sensitivity) and blood pressure at 50% maximal heart rate (P50) were calculated. MAIN RESULTS: Baroreflex sensitivity was found to increase from birth to six weeks of age (P < 0.0001), with the most rapid changes occurring after two weeks of age. Increasing age was accompanied by shift of the baroresponse curve to an increased range of heart rate changes at higher blood pressures. Maximal heart rates did not differ with advancing postnatal age. CONCLUSIONS: Swine baroreflex sensitivity increases from birth to six weeks of age, with higher blood pressures causing greater bradycardia in older piglets. These findings are consistent with postnatal maturation of the cardiovascular autonomic nervous system.

Age Factors↗
PubMedDate not supplied

Cerebral arteriovenous malformation: prenatal and postnatal central blood flow dynamics.

Using the Doppler technique, this study compared the prenatal and postnatal flow patterns of an infant with cerebral arteriovenous (AV) malformation. Fetal right ventricular end-diastolic dimension was 1.7 cm with right ventricular ejection equaling 66% of the combined cardiac output. Diastolic flow was reversed in the fetal aortic isthmus but forward-moving in the descending aorta, resulting in a watershed phenomenon. In the carotid arteries an increased forward diastolic flow was noted while the internal jugular vein exhibited a pulsatile arterial type of flow. The pulsatility index of the umbilical artery was normal. After birth and closure of the ductus arteriosus, the output from both ventricles was equally increased, and retrograde diastolic flow was then observed in the descending aorta. In conclusion, specific fetal features of cerebral AV malformation are increased right ventricular output probably related to the increased superior vena cava return, watershed phenomenon in the descending aorta causing the right ventricle to perfuse both the lower and upper body, and preserved umbilical circulation.

Adult↗