Early changes in collateral blood flow to ischemic myocardium and their influence on bimodal vulnerability during the first 30 min of acute coronary artery occlusion in dogs

Abstract

Coronary collateral blood flow and its changes during the first 30 min of acute coronary artery occlusion were studied in 34 anesthetized dogs to clarify its influence on the vulnerability of the heart in this first arrhythmic phase. Collateral flow was determined with 9-micron tracer microspheres (TM) injected at 1, 10 and 30 min after acute proximal occlusion of the left circumflex (LCX, n = 30) or left anterior descending (LAD, n = 4) coronary artery. The post-mortem selective retrograde coronary angiography was used to evaluate the functional extent of preexisting coronary collaterals. After acute LCX occlusions collateral flow increased significantly (p less than 0.05) from 17.8 +/- 2.7 ml.(min.100 g)-1 (mean +/- SE; n = 13) at 1 min to 29.3 +/- 5.1 ml . (min . 100 g)-1 at 30 min of occlusion in animals with well-formed preexisting coronary collaterals (group 1), whereas it was very low (4.7 +/- 0.6 ml . (min . 100 g)-1; n = 13) and changed only slightly in dogs with poor collaterals (group 2). Most of these animals died by ventricular fibrillation (VF) before a second measurement could be carried out. In four dogs with poor collaterals but an unusually small LCX area (group 3), flow remained almost constant (11.0 +/- 4.7 versus 11.0 +/- 4.4 ml . (min . 100 g)-1) during this period. Similar results were obtained in animals with acute LAD occlusion (group 4). Ventricular extrasystoles (VES) mainly developed in animals with poor collaterals and respective low and almost unchanging collateral flow (group 2,3,4) while none or only a few VES occurred in dogs in which flow initially was clearly higher and increased significantly (group 1). The animals of group 1, 3 and 4 all survived the first arrhythmic phase, whereas all the animals of group 2 died by VF, either in the arrhythmic subphase Ia (n = 7) or Ib (n = 6). The results of the present study show that only the initial magnitude of flow is decisive for the development of VES and VF during the first arrhythmic phase, whereas the subsequent increase in flow is of no importance to the bimodal vulnerability in the first arrhythmic phase (subphases Ia and Ib). The in vivo measured critical minimal collateral flow of about 5 ml . (min . 100 g)-1 corresponds well with the survival limit (border between collateral state III and IV) previously determined by post-mortem retrograde coronary angiography.

Pentobarbital versus medetomidine-ketamine-fentanyl anaesthesia: effects on haemodynamics and the incidence of ischaemia-induced ventricular fibrillation in swine

“…However, in the present study, swine anaesthetized with medetomidineketamine-fentanyl showed a substantially higher incidence of ischaemia-induced ventricular brillation than swine anaesthetized with pentobarbital. This nding cannot be ascribed to differences in known determinants of ischaemia-induced ventricular brillation such as pre-ischaemic heart rate (Wainwright & Parratt 1993), body temperature (Mouritzen & Andersen 1966, Mortensen et al 1993, size of ischaemic area (Verdouw & Hartog 1986), collateral blood ow (Yoshida & Downey 1986, von Mutius et al 1988, and arterial pH (Dong et al 1967). A positive correlation between pre-ischaemic heart rate and occurrence of VF during ischaemia has been shown in swine (Wainwright & Parratt 1993).…”

The Effect of Physical Activity on VEGF and HIF-1 Signaling

“…VEGF R1 (Flt-1) plasma soluble form binds to VEGF plasma and is of particular importance as a functional regulator of angiogenesis. VEGF regulates inflammatory responses, angiogenesis, and vasculogenesis through VEGF R1 and VEGF R2 mediators (8).…”

Innate collateral segments are predominantly present in the subendocardium without preferential connectivity within the left ventricular wall

“…; von Mutius et al . ). This is in agreement with observations in patients with long‐standing coronary artery disease, where only in approximately one‐quarter to one‐third of the cases was collateral function sufficient to prevent ischaemia during brief coronary occlusion (Wustmann et al .…”