Paula Weinberg

Decreased heart rate variability in panic disorder patients: A study of power-spectral analysis of heart rate

We have previously found decreased standard deviations and mean consecutive differences of R-R intervals in panic disorder patients in standing posture, compared with control subjects. In the present study, we used spectral analysis of heart rate variability to examine autonomic function in 21 panic disorder patients and 21 normal control subjects. Patients had a significantly lower standard deviation of heart rate in supine as well as standing postures. Absolute low frequency power (0.01-0.05 Hz) was also significantly lower in panic disorder patients in standing postures. Upon standing, the panic disorder patients had significantly higher relative mid-frequency power (0.07-0.15 Hz). During a standing deep-breathing condition at six breaths per minute, the patients had a significantly decreased absolute and relative mid-frequency (0.07-0.15 Hz) power compared with control subjects. These findings suggest a decrease in cholinergic and a relative increase in adrenergic responsiveness in panic disorder patients compared with control subjects.

Effect of imipramine treatment on heart rate variability measures

Recently, heart rate (HR) variability has received considerable attention, and a decreased HR variability has been linked to a significant risk of cardiovascular illness. We have previously reported such a decreased variability in panic disorder patients. In this study, we report on HR variability in 12 depressed and 6 panic disorder patients at baseline and 1 and 3 weeks of treatment with imipramine as measured by the standard deviation, mean consecutive difference and the standard deviation of the mean consecutive difference of the R-R intervals in supine, supine deep breathing and standing postures. In all subjects, imipramine (mean dose: 70 mg/day) produced a significant decrease in heart rate variability at week 3 as measured by the above variables. This decrease in HR variability during imipramine treatment is probably due to its anticholinergic effects.

Effects of yohimbine on heart rate variability in panic disorder patients and normal controls: A study of power spectral analysis of heart rate

Summary: We studied the effects of yohimbine on heart rate (HR) variability in 13 normal controls and 13 patients with panic disorder. Yohimbine produced a significant increase in SD of HR in standing posture in both patients (p = 0.01) and normal controls (p = 0.025). Panic disorder patients had a significant increase in standing absolute midfrequency (MF) power (0.07–0.15 Hz) after administration of yohimbine (p = 0.002). The ratio of post- to preyohimbine standing MF power (0.07–0.15 Hz) during standing was significantly higher in patients as compared with controls (2.3 ± 1.08 vs. 1.33 ± 0.38; p = 0.01), which suggests an increased responsivity of panic disorder patients to the adrenergic effects of yohimbine

Isoproterenol-induced panic attacks

Eighty-six panic disorder patients and 45 nonpsychiatric controls were infused with isoproterenol at a rate of 1 microgram/min for up to 20 min in a placebo-controlled, double-blind study. Sixty-six percent of panic disorder patients experienced panic attacks during isoproterenol infusions, compared to 16% during placebo infusions. Nine percent of control subjects panicked with isoproterenol, but none panicked with placebo. Patients were more sensitive than controls to the anxiogenic effects of isoproterenol, as measured by subject self-ratings on a panic description scale. The frequency of panic attacks induced in patients was related to the dosage of isoproterenol; 79% of the patients who received a mean of 18.5 ng/min/kg of isoproterenol panicked. The panic attacks experienced by patients during isoproterenol infusions were similar to those experienced during placebo infusions.

Lactate- and isoproterenol-induced panic attacks in panic disorder patients and controls.

In a double-blind study using sodium lactate and isoproterenol infusions to provoke panic attacks, 73 of 86 panic disorder patients and 10 of 45 controls panicked with lactate, and 58 of 86 patients and 4 of 45 controls panicked with isoproterenol. We measured baseline and peak anxiety ratings in 10 controls with lactate-induced panic attacks, 31 controls who did not panic during lactate infusions, and 63 panic disorder patients who did panic during lactate infusions. The controls who panicked with lactate had robust increases in their anxiety ratings very similar to the increases experienced by patients who panicked with lactate.

Preinfusion anxiety predicts lactate-induced panic attacks in normal controls.

&NA; Preinfusion anxiety, heart rate, and blood pressure were measured in 31 normal subjects who received sodium lactate infusions. Eight subjects developed symptoms of panic anxiety during these infusions. Preinfusion anxiety as measured by psychologic symptoms of anxiety on the Panic Description Scale was significantly higher in the panickers while heart rate and blood pressure were not.

Imipramine-induced jitteriness and decreased serum iron levels.

Jitteriness appears to be a specific side effect of tricyclic antidepressant treatment in panic disorder patients. In addition, the patients with jitteriness have lower serum iron levels compared to those that do not develop jitteriness (p = 0.01).

Thyroid hormone levels in panic disorder.

A history of thyroid dysfunction has been reported in patients with phobic disorders. There is also evidence of a blunted TSH response to TRH stimulation in patients with panic disorder. In this study, values of T3, T4 and T7 were compared between 26 patients with panic attacks and 20 normal controls. Patients were diagnosed according to DSM-III criteria and those with a clinical history of thyroid dysfunction were excluded. Patients were not on any medication when the blood samples were drawn. The mean values of T3, T4 and T7 did not significantly differ between the two groups, suggesting no evidence of hypo or hyperthyroidism; however, the variance of distribution of T3, T4 and T7 values was significantly different between the two groups (Fmax values for T3: 2.55, p value < 0.05; T4: 3.15, p value < 0.01; T7: 2.55, p value < 0.05).

Do higher preinfusion heart rates predict laboratory-induced panic attacks?

Baseline and preinfusion heart rates of 13 panic disorder patients who panicked during a placebo infusion were not significantly different from those of 57 panic disorder patients who did not panic during a placebo infusion. The change in preinfusion heart rates from baseline values also was not significantly different between the two groups.

Leftward Shift of R-Axis on Electrocardiogram in Patients with Panic Disorder and Depression

In a prospective study, we have compared R-axis on routine electrocardiograms of panic disorder patients (n = 52) with that of depressed patients (n = 41) and normal controls (n = 65). All subjects were physically healthy and were normotensive. There was a significant leftward shift of R-axis in both depressed and panic disorder patients compared to normal controls. The implications of these findings are discussed.