Genuine effects of ventricular fibrillation upon myocardial blood flow, metabolism and catecholamines in patients with aortic stenosis.
OBJECTIVE
Ventricular fibrillation (VF) is life-threatening because of its haemodynamic and metabolic effects. The purpose was to examine if VF also has primary effects per se. We therefore investigated the early effects of VF on myocardial blood flow, metabolic characteristics and catecholamine concentrations in patients undergoing surgery for aortic stenosis.


METHODS
The immediate effects of up to 5 min of VF were studied in 21 patients during cardiopulmonary bypass (CPB) before valve replacement.


RESULTS
During VF the global myocardial oxygen consumption, coronary blood flow and vascular resistance were unchanged, and the mean arterial pressure (on CPB) decreased from 70 to 51 mmHg (p < 0.02). Fibrillation induced a high myocardial tone and a probable functional aortic insufficiency, which instantly equilibrated left ventricular and aortic pressures. Signs of myocardial ischaemia and acidosis developed after 4 min: a decrease in the pH of coronary sinus blood from 7.38 to 7.32 (p < 0.001), an increased release of lactate from 32 to 137 micromol/min (p < 0.001) and potassium from 29 to 73 micromol/min (p < 0.05). The noradrenaline net release increased from 0.021 to 0.58 nmol/min (p < 0.02) after 1.5 min of VF and then decreased. The adrenaline net uptake remained low and unchanged (17-28%).


CONCLUSIONS
VF in patients with aortic stenosis was rapidly followed by myocardial ischaemia, acidosis and a transient increase in the myocardial noradrenaline net release despite sufficient coronary perfusion and unchanged global myocardial oxygen consumption. The VF instantly induced equilibration of left ventricular and aortic pressure and probably caused a relative underperfusion of the subendocardium. These factors all support persistence of VF.
Sandstedt
Bengt
B
Division of Cardiology, Sahlgrenska University Hospital, SE-413 45 Göteborg, Sweden. bengt.sandstedt@swipnet.se
Pontén
Johan
J
Olsson
S Bertil
SB
Edvardsson
Nils
N
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001024:Aortic Valve Stenosis / Q000000981:diagnostic imaging / Q000601:surgery*; D001783:Blood Flow Velocity; D002315:Cardiopulmonary Bypass / Q000009:adverse effects / Q000379:methods; D002395:Catecholamines / Q000032:analysis / Q000378:metabolism*; D015150:Echocardiography, Doppler; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D019918:Heart Valve Prosthesis Implantation / Q000009:adverse effects* / Q000379:methods; D006801:Humans; D007431:Intraoperative Complications / Q000175:diagnosis*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000175:diagnosis* / Q000378:metabolism; D011336:Probability; D011446:Prospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D015996:Survival Rate; D016896:Treatment Outcome; D014655:Vascular Resistance / Q000502:physiology; D014693:Ventricular Fibrillation / Q000150:complications / Q000175:diagnosis*
D002395:Catecholamines