RESUMEN
BACKGROUND: The acute bradycardia induced by the occlusion of an arteriovenous fistula (AVF), known as the Nicoladoni-Branham sign, is considerably larger than that which occurs during carotid sinus massage. This suggests increased arterial baroreflex sensitivity during acute AVF occlusion. Moreover, the influence of acute AVF occlusion on muscle sympathetic nerve traffic (MSNA, by microneurography) is unknown. We therefore assessed the effects of acute AVF occlusion on baroreflex sensitivity and on MSNA in patients with stable functional kidney grafts and patent AVF. METHODS: We measured blood pressure (BP), MSNA (n = 11), heart rate (HR), cardiac output (CO) and arterial baroreflex sensitivity (n = 18) at baseline and during acute, 30-s pneumatic AVF occlusions in 23 renal transplanted recipients. RESULTS: During the first 5 s of the AVF occlusion, mean BP increased from 98+/-4 to 112+/-4 mmHg (P<0.0001) while MSNA decreased to 28+/-5% of baseline values (P<0.0001) and HR decreased from 71+/-3 to 61+/-3 b.p.m. (P<0.0001). The largest increases in BP were accompanied by the most marked decreases in MSNA (r = -0.79, P = 0.003) and HR (r = -0.49; P = 0.01) during the first 5 s of the AVF occlusion. During AVF occlusion baseline CO of 6.9+/-0.3 decreased to 5.6+/-0.3 l/min (P<0.0001) while baroreflex sensitivity increased from 10+/-1 to 17+/-2 ms/mm Hg (P<0.001). CONCLUSIONS: Arterial baroreceptor activation and increased arterial baroreflex sensitivity decrease heart rate during AVF occlusion. In addition, our study is the first to demonstrate that arterial baroreflex activation decreases sympathetic nerve traffic during the Nicoladoni-Branham sign.
Asunto(s)
Fístula Arteriovenosa , Barorreflejo/fisiología , Trasplante de Riñón/fisiología , Músculo Liso/inervación , Sistema Nervioso Simpático/fisiología , Presión Sanguínea/fisiología , Bradicardia/fisiopatología , Gasto Cardíaco/fisiología , Femenino , Frecuencia Cardíaca/fisiología , Humanos , Masculino , Persona de Mediana Edad , Músculo Liso/fisiologíaRESUMEN
BACKGROUND: Left ventricular hypertrophy and dilatation is a frequent finding in kidney transplant recipients, which may be favored by the persistent patency of arteriovenous fistula. The purpose of the current study was to prospectively investigate whether surgical closure of the fistula allows reduction of abnormalities of left ventricular morphology in stable renal transplant patients. Furthermore, we studied the ability of preoperative echocardiographic and noninvasive hemodynamic measurements, including the effects of a temporary occlusion of the fistula, to predict postoperative left ventricular diameter and mass reduction. METHODS: Seventeen kidney transplant recipients referred for surgical arteriovenous fistula closure were prospectively studied. Standard echocardiographic parameters, heart rate, and blood pressure were assessed preoperatively at baseline and during an acute pneumatic fistula occlusion. These measurements were repeated 3 to 10 weeks after surgical closure. Six kidney transplant recipients with patent arteriovenous fistulas referred for routine echocardiographic follow-up served as a control group. RESULTS: Surgical fistula closure decreased left ventricular end-diastolic diameter and mass indexes (29.9+/-2.4 to 27.4+/-2.1 mm/m2, P<0.001, and 141+/-37 to 132+/-39 g/m2, P<0.05, respectively), whereas no changes were seen in controls after a similar delay. Postoperative left ventricular end-diastolic diameter and mass reductions correlated best with the increases in total peripheral resistance (r=0.85, P<0.0001) and mean arterial blood pressure (r=0.64, P=0.006) during pneumatic occlusion, respectively. CONCLUSIONS: Surgical closure of arteriovenous fistula reduces left ventricular diameter and mass in kidney transplant recipients. Increases in blood pressure and total peripheral resistance induced by temporary fistula occlusion are the best predictors of these morphological changes.