Decreased Heart Rate Variability in Congestive Heart Failure
heart rate variability only serves to further cloud this issue.
In the May 15,199 1 issue, Casolo et al,’ using power spectral analysis techniques, reported that “heart rate variability is greatly reduced in patients with congestive heart failure.” However, their study group consisted of 15 patients with decreased left ventricular function secondary to coronary artery disease (CAD). The investigators mistakenly stated that the study by Kleiger et al2 demonstrated that “heart rate variability is a powerful independent prognostic factor in patients with CAD.” Kleiger, however, studied heart rate variability only in patients with CAD who had sustained myocardial infarction. The independent association between heart rate variability and CAD is unknown. Other investigators have attempted to understand this relation, but the results are conflicting. Hayano et a1,3,4 using the “coefficient of component variance,” have shown in 2 reports that decreased vagal tone is correlated with the extent and severity of CAD. Rich et aLs defining heart rate variability as the “standard deviation of Sminute means of sinus cycle lengths,” did not find this to be the case. Therefore, it would be of great interest to know the degree of CAD in Casolo’s subjects. It is well known that myocardial ischemia and infarction influence neural activity in the heart independent of their effect on left ventricular function.6 Thus, Casolo’s study group had 2 potential reasons for alteration of the sympathovagal balance. It is not clear from the presented data whether the pathologic process of congestive heart failure or CAD exerted a greater effect on autonomic tone. Furthermore, the absence of a standard definition of Letters (from the United States) concerning a particular article in the Journal must be received within 2 months of the article’s publication, and should be limited (with rare exceptions) to 2 doublespaced typewritten pages. Two copies must be submitted.
286
THE AMERICAN
JOURNAL
measures of pump failure. Thus, HR variability is decreased in paJames E. Carter, Jr., MD tients with CHF and it is also assoChicago, Illinois ciated with decreased left ventricu29 May 1991 lar function. With regard to Carter’s question, 1. Casolo G, Balli E, Fazi A, Gori C, in our more recent study,4 all paFreni A, Gensini G. Twenty-four-hour tients had multivessel CAD. In parspectral analysis of heart rate variability ticular, 12 patients had 3-vessel and in congestive heart failure secondary to the remaining three 2-vessel discoronary artery disease. Am J Cardiol ease. 1991;67:1154-1158. 2. Kleiger RE, Miller JP, Bigger JT, Conflicting data6T7 regarding the Moss AJ, and the Multicenter Post-Inrelation between HR variability farction Research Group. Decreased and degree of CAD may depend on heart rate variability and its association several factors. Differences in with increased mortality after acute myomethodology and selection of pacardial infarction. Am J Curdiol 1987; tients may account for the results of 59:256-262. the cited studies. For example, Rich 3. Hayano J, Sakakibara Y, Yamada M, et al6 used the standard deviation Ohte N, Fujinami T, Yokoyama K, Waof 5 minute means of sinus cycle tanabe Y, Takata K. Decreased magnitude of heart rate spectral components in lengths in milliseconds, and the coronary artery disease: its relation to an- mean left ventricular ejection fracgiographic severity. Circulation 1990;s 1: tion of their study group was 65 f 1217-1224. 14%. Hayano et al7 used the high4. Hayano J, Yamada A, Mukai S, Sakafrequency component of spectral kibara Y, Yamada M, Ohte N, Hashicomposition of HR variability as a moto T, Fujinami T, Takata K. Severity measure of “pure” vagal activity, of coronary atherosclerosis correlates and the mean left ventricular ejecwith the respiratory component of heart tion fraction of their patients was rate variability. Am Heart J 1991;121: significantly decreased with the ad1070-1079. vancing severity of CAD. In fact, it 5. Rich MW, Saini JS, Kleiger RE, Carcannot be excluded that the apparney RM, teVelde A, Freedland KE. Correlation of heart rate variability with clinently conflicting results of these 2 ical and angiographic variables and late investigations may be explained mortality after coronary angiography. specifically by a difference in the Am J Cardiol 1988;62:714-717. left ventricular function of the pa6. Zipes DP. Influence of myocardial tients studied. ischemia and infarction on autonomic inNeural activity of the heart can nervation of heart. Circulation 1991;82: be influenced by several different 1095-l 105. factors including acute myocardial ischemia and infarction, left ventricular dysfunction, diabetic autoREPLY: The comments made by nomic neuropathy, and so forth. With regard to the specific point Carter raise several interesting points of discussion. Although it is raised by Carter, although it is not clear whether the presence and theoretically possible that ischemia extent of coronary artery disease and infarction may play a major (CAD) affect heart rate (HR) vari- role in the impaired neural activity ability, it is generally accepted that of the heart observed during CHF, HR variability is decreased in con- it is, however, difficult to differentigestive heart failure (CHF).‘*2 Al- ate the effect of CHF, per se, from though designed for different pur- that of a primary neural impairposes, other studies using HR spec- ment (for example, purely “ischtral analysis showed that the total emit”). Frequently, CHF seconpower of HR variability spectra (a dary to CAD is the result of 1 or measure of HR variability) is great- more previous infarcts, and there ly reduced in patients with CHF are no studies comparing HR varicompared with normal subjects.3*4 ability in CHF secondary to CAD Also, in Kleiger et al’s5 study, HR with that in CAD without CHF. In variability was inversely and signif- a previous study’ we did not find icantly correlated with all available any difference in HR variability be-
OF CARDIOLOGY
VOLUME
69
JANUARY
15,
1992
heart rate variability only serves to further cloud this issue.
In the May 15,199 1 issue, Casolo et al,’ using power spectral analysis techniques, reported that “heart rate variability is greatly reduced in patients with congestive heart failure.” However, their study group consisted of 15 patients with decreased left ventricular function secondary to coronary artery disease (CAD). The investigators mistakenly stated that the study by Kleiger et al2 demonstrated that “heart rate variability is a powerful independent prognostic factor in patients with CAD.” Kleiger, however, studied heart rate variability only in patients with CAD who had sustained myocardial infarction. The independent association between heart rate variability and CAD is unknown. Other investigators have attempted to understand this relation, but the results are conflicting. Hayano et a1,3,4 using the “coefficient of component variance,” have shown in 2 reports that decreased vagal tone is correlated with the extent and severity of CAD. Rich et aLs defining heart rate variability as the “standard deviation of Sminute means of sinus cycle lengths,” did not find this to be the case. Therefore, it would be of great interest to know the degree of CAD in Casolo’s subjects. It is well known that myocardial ischemia and infarction influence neural activity in the heart independent of their effect on left ventricular function.6 Thus, Casolo’s study group had 2 potential reasons for alteration of the sympathovagal balance. It is not clear from the presented data whether the pathologic process of congestive heart failure or CAD exerted a greater effect on autonomic tone. Furthermore, the absence of a standard definition of Letters (from the United States) concerning a particular article in the Journal must be received within 2 months of the article’s publication, and should be limited (with rare exceptions) to 2 doublespaced typewritten pages. Two copies must be submitted.
286
THE AMERICAN
JOURNAL
measures of pump failure. Thus, HR variability is decreased in paJames E. Carter, Jr., MD tients with CHF and it is also assoChicago, Illinois ciated with decreased left ventricu29 May 1991 lar function. With regard to Carter’s question, 1. Casolo G, Balli E, Fazi A, Gori C, in our more recent study,4 all paFreni A, Gensini G. Twenty-four-hour tients had multivessel CAD. In parspectral analysis of heart rate variability ticular, 12 patients had 3-vessel and in congestive heart failure secondary to the remaining three 2-vessel discoronary artery disease. Am J Cardiol ease. 1991;67:1154-1158. 2. Kleiger RE, Miller JP, Bigger JT, Conflicting data6T7 regarding the Moss AJ, and the Multicenter Post-Inrelation between HR variability farction Research Group. Decreased and degree of CAD may depend on heart rate variability and its association several factors. Differences in with increased mortality after acute myomethodology and selection of pacardial infarction. Am J Curdiol 1987; tients may account for the results of 59:256-262. the cited studies. For example, Rich 3. Hayano J, Sakakibara Y, Yamada M, et al6 used the standard deviation Ohte N, Fujinami T, Yokoyama K, Waof 5 minute means of sinus cycle tanabe Y, Takata K. Decreased magnitude of heart rate spectral components in lengths in milliseconds, and the coronary artery disease: its relation to an- mean left ventricular ejection fracgiographic severity. Circulation 1990;s 1: tion of their study group was 65 f 1217-1224. 14%. Hayano et al7 used the high4. Hayano J, Yamada A, Mukai S, Sakafrequency component of spectral kibara Y, Yamada M, Ohte N, Hashicomposition of HR variability as a moto T, Fujinami T, Takata K. Severity measure of “pure” vagal activity, of coronary atherosclerosis correlates and the mean left ventricular ejecwith the respiratory component of heart tion fraction of their patients was rate variability. Am Heart J 1991;121: significantly decreased with the ad1070-1079. vancing severity of CAD. In fact, it 5. Rich MW, Saini JS, Kleiger RE, Carcannot be excluded that the apparney RM, teVelde A, Freedland KE. Correlation of heart rate variability with clinently conflicting results of these 2 ical and angiographic variables and late investigations may be explained mortality after coronary angiography. specifically by a difference in the Am J Cardiol 1988;62:714-717. left ventricular function of the pa6. Zipes DP. Influence of myocardial tients studied. ischemia and infarction on autonomic inNeural activity of the heart can nervation of heart. Circulation 1991;82: be influenced by several different 1095-l 105. factors including acute myocardial ischemia and infarction, left ventricular dysfunction, diabetic autoREPLY: The comments made by nomic neuropathy, and so forth. With regard to the specific point Carter raise several interesting points of discussion. Although it is raised by Carter, although it is not clear whether the presence and theoretically possible that ischemia extent of coronary artery disease and infarction may play a major (CAD) affect heart rate (HR) vari- role in the impaired neural activity ability, it is generally accepted that of the heart observed during CHF, HR variability is decreased in con- it is, however, difficult to differentigestive heart failure (CHF).‘*2 Al- ate the effect of CHF, per se, from though designed for different pur- that of a primary neural impairposes, other studies using HR spec- ment (for example, purely “ischtral analysis showed that the total emit”). Frequently, CHF seconpower of HR variability spectra (a dary to CAD is the result of 1 or measure of HR variability) is great- more previous infarcts, and there ly reduced in patients with CHF are no studies comparing HR varicompared with normal subjects.3*4 ability in CHF secondary to CAD Also, in Kleiger et al’s5 study, HR with that in CAD without CHF. In variability was inversely and signif- a previous study’ we did not find icantly correlated with all available any difference in HR variability be-
OF CARDIOLOGY
VOLUME
69
JANUARY
15,
1992
