Intravenous cocaine decreases cardiac vagal tone, vagal index (derived in Lorenz space), and heart period complexity (approximate entropy) in cocaineabusers

We assessed the effects of i.v. cocaine on parasympathetic and sympathetic nervous system activity, and on the complexity vs. regularity of changes in heart rate over time. Fourteen otherwise healthy men with histories of i.v . cocaine abuse received bolus injections of cocaine (20 mg or 40 mg) and p lacebo (saline) on different days. Cardiovascular measures derived from the electrocardiogram. including heart rate, Forges' vagal forts (respiratory sinus arrhythmia), the 0.10 Hz rhythm, Toichi's vagal index, Toichi's sympa thetic index, and approximate entropy (ApEn), were measured continuously. A s predicted, cocaine produced tachycardia, accompanied by pronounced decrea ses in response to 40 mg cocaine in two different vagal tone indexes that p recisely mirrored Nle increases ill heart rate. The measure of sympathetic (and vagal) neural( influences on the heart (0.10 Hz wave) also decreased i n response to cocaine. Converging evidence from Toichi's vagal index suppor ted the conclusion that fire tachycardia from cocaine was due to withdrawal ,nl of cardiac vagal tone. These findings, and evidence that cocaine decrea sed cardiovascular complexity, contradict the prevailing assumption that th e mechanism by rc,which cocaine produces tachycardia is sympathetic (beta-a drenergic). We discuss implications for cardiac arrhythmias associated with cocaine abuse and death dire to overdose. Published by Elsevier Science In c.