for “pure” parasystole. They also observed that these rules were also fulfilled in some sporadic casesreported by other investigators. The mathematic relation under consideration symmetry - was found in all our patients.3Precisely,its identification, not the exact moment at which parasytole wasdiagnosed,was consideredasthe starting point of the current study. However, initial symmetry did not last for long periods of time (only minutes), consideringthat the tracings wereobtained for 24 hours. A reviewof the tapes showedthat the lost symmetry resultedfrom the fact that the physiologic parameters tended to change as time went by. Of the 3 pertinent parameters, we have observed that in absenceof exit block, refractory periods tended to be constant. Yet, sinuscycle length and ectopic cycle length (the former more than the latter) were seen to be changing variables. In fact, it is well known that sinus cycle lengths show frequent fluctuations. Moreover, parasystolic cycle lengths are also not constant,but lessso than the former.5 Although not analyzed as such in this study, it is possibleto consider that during a 24hour period parasystoleshowsnot 1 but severalsymmetries, with the correspondingnumbers depending on the

Effects of Amiodarone

different values that the changing parameters attain throughout the monitoring time (Figures 2 and 4). Finally, in our patients, the possibility that the arrhythmia diagnosed as “pure” parasystole may have been parasystole with “weak” modulation cannot be completelyexcluded.Becausethere were somevariations in parasystolic cycle lengths during the overall (longterm) recording time, fluctuations attributed to changes in the timing of automatic dischargescould have reflectcd lesserdegreesof modulation than degreesof variations of automaticity. However, this in no way would invalidate our study since, as previously mentioned, “weak” modulation may obey the rules of pure parasytole.2,4 1. GlassL, GoldbergerAL, Belair J. Dynamicsof pure parasystole.Am J Physiol 1986;251:H841-H847. 2. Gordon D, Scagliotti D, CourtemancheMT Glass L. A clinical study of the dynamicsof parasystole.PACE 1989;12:1412-1418. 3. Kaku M, Trainer J. Beyond Einstein. The cosmicquest for the theory of the universe. New York: Bantam Books, 1987;109:121-123. 4. CourtemancheM, Glass L, RosengartenMD, Goldberger AL. Beyond pure parasystole:promisesand problems in modeling complex arrhythmias. Am J Physiol 1989;257:H693-H706.

5. Scherf D, Schott A. Extrasystolesand Allied Arrhythmias. 2nd ed. Chicago: Year Book Medical Publishers, 1973:271-272.

6. Hawking SW. A Brief History of Time. New York: Bantam Books, 1988;71.

on Serum Lipoprotein

Levels

Stewart G. Albert, MD, Larry E. Alves, MD, and Edward P. Rose, MD miodarone is an antiarrhythmic agent approved for the treatment of recalcitrant ventricular arrhythmias. It is an amphiphilic-iodinated organic compound with a prolonged elimination rate, and has beenassociatedwith a high incidenceof thyroid dysfunction.’ In a previous evaluation of the effects of amiodarone, serum cholesterol was monitored as a systemic marker for thyroid dysfunction.2 Unexpectedly, there were uniform increasesin serum cholesterolindependent of thyroid hormone status. Controversy exists as to whether there are changesin serum cholesterollevelsin patients receiving amiodarone,2-6and it is important to define the action of this drug on high-risk patients who already have heart disease.

A

Twenty-seven patients (I 5 men and I2 women: 18 with paroxysmal ventricular tachycardia, 6 with multiform ventricular arrhythmias associated with arteFrom the Divisions of Endocrinology and Cardiology, Department of Internal Medicine, St. Louis University School of Medicine, 1402 South Grand Boulevard, St. Louis, Missouri 63104, and the Department of Internal Medicine, Memorial Hospital, Belleville, Illinois. Manuscript received December 17, 1990; revised manuscript received March 11, 1991, and accepted March 18.

riosclerotic cardiovascular disease and 3 with symptomatic atrialflbrillation; mean age f standard error of the mean 70 f 2 years) who required amiodarone for the control of severe symptomatic arrhythmias were followed prospectively. The clinical procedures for monitoringfor efficacy and adverse reactions were described previously.2 Amiodarone was given at a loading dose of 400 to 600 mg/day initially followed by a maintenance dose of 200 mg/day. If the arrhythmia was refractory as assessed by electrocardiography and ambulatory monitoring or by exercise testing, the initial dose was repeated. When necessary the maintenance dose was titrated upward. The maintenance dose was also adjusted downward according to adverse side effects, predominantly symptomatic bradycardias. Many patients with arteriosclerotic cardiovascular disease had underlying hypercholesterolemia, and 3 had been receiving stable doses of gemfibrozil; 3 had started receiving lovastatin either previously (n = I) or at baseline (n = 2) concomitantly with the amiodarone. Fifteen subjects were receiving thiazides and 2 were receiving estrogens; these medications were started before the amiodarone and

BRIEF REPORTS 259

20 0 -20 -40 -60 -80 50

,,

0-l0

1

-100

I

-120 3

9

12

Total

I LDL Cholesterol

HDL

M:tlttls FIGURE 1. The effect of amiodarone on lipoprotein levels. Total (closed circles), low-density lipoprotein (closed squares), and high-density lipoprotein (open circles) cholesterol were determined at baseline (n = 20), 3 months (n = lo), 6 months (n = 15) and 12 months (n = 11) in patients receiving amiodarone. Values shown are mean f standard error of the mean. “p 165 > 160 > 155 >150 >145 >140 >135 >130 2125 >120 >115 >llO >lOO

13 14 15 16 22 22 24 26 29 31 33 37 37 39 44

3 3 5 5 6 6 8 8 10 12 13 13 17 17 23

0.28 0.30 p.33 0.35 0.48 0.52 0.57 0.63 0.67 0.72 0.80 0.80 0.80 0.85 0.96

0.89 0.89 0.82 0.82 0.79 0.79 0.71 0.71 0.64 0.57 0.54 0.54 0.39 0.39 0.18

0.51 0.53 0.51 0.53 0.59 0.59 0.59 0.62 0.64 0.64 0.65 0.70 0.65 0.68 0.66

ECG = electrocardiographic;

LV = l&ventricle.

BRIEF REPORTS 261

Effects of amiodarone on serum lipoprotein levels.

for “pure” parasystole. They also observed that these rules were also fulfilled in some sporadic casesreported by other investigators. The mathematic...
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