احساس ضربان قلب در اختلال پانیک: تحلیل مجدد

This article describes a reanalysis of seven studies on heart beat perception (HBP) in panic disorder. The pooled sample had 709 participants from eight diagnostic categories. Accurate HBP was uncommon, but more prevalent among panic disorder patients than among healthy controls, depressed patients, patients with palpitations and individuals with infrequent panic attacks. No differences were found between panic disorder patients and patients with other anxiety disorders. Accurate perceivers had higher anxiety sensitivity scores than inaccurate perceivers. The data remain inconclusive as to whether perceived heart rate is correlated with anxiety in inaccurate perceivers. Physical exercise, distraction, variations in instructions and treatment each influenced HBP. However, the influence was different than previously thought. Finally, it is suggested that HBP may be understood in terms of schema-guided information processing.

There has been some controversy regarding the question of whether patients with panic disorder are better at perceiving their own heartbeats than are other groups. In a heartbeat perception (HBP) task, participants are asked to silently count all heartbeats they feel in their body, without taking their pulse. This procedure is known as `mental tracking' (Schandry, 1981). Various other procedures exist to measure HBP, e.g. asking subjects to choose their own heart rhythm from a number of series of tone pips (e.g. Brener & Kluvitse, 1988). However, because the `mental tracking' procedure is the only procedure that has yielded significant differences between panic disorder patients and other groups, this article will only concern studies that used this procedure. In the first of these studies, Ehlers and Breuer (1992)showed that panic disorder (PD) patients perform better on this test than normal controls, infrequent panickers and patients with specific phobias. Test performance can be expressed in a continuous score (percentage error) or in a dichotomous score (accurate/nonaccurate, using a criterion of maximum difference between actual and counted beats). The above findings appeared with both types of scores. In a second study, both panic disorder and generalized anxiety disorder patients had lower percentage error scores than depressed patients (Ehlers and Breuer, 1992). These results were replicated by Ehlers et al., (1995). In this latter study, panic disorder patients again had a significantly lower error score than controls. The group difference was also significant in a second condition, when a series of distracting tones was presented during the task. However, during a third, strict instruction condition (`count only those heartbeats about which you are sure') no group differences emerged. The findings gained clinical relevance in a study by Ehlers (1995), that showed that good HBP was predictive of poor treatment outcome and of recurrence of panic attacks after initial remission. However, Antony et al. (1995)failed to find differences in HBP among groups of patients with panic disorder, patients with social phobia and normal controls. The error scores of the PD and control group were quite comparable to Ehlers et al., (1995), but with less statistical power the difference was not significant. Furthermore, the social phobics had identical scores to the PD patients. Barsky et al., (1994)studied three groups: two groups of patients who were referred to ECG monitoring for the evaluation of palpitations (groups with and without panic disorder) and a normal comparison group. Results showed that palpitation patients with PD were not more accurately aware of their heartbeats than nonpanic palpitation patients or controls. Recently, Van der Does et al., (1997)found no differences in error scores among patients with panic disorder, depressed patients and normal controls. The above reviewed studies are summarized in Table 1. Table 1. Summary of the results of mental tracking studies Reference Participants % Error (SD) Contrasts Ehlers and Breuer (1992)study 2 panic disorder (N=65) 22.1 (17.8) PD lower error scores than all other groups infrequent Panic (N=50) 29.2 (18.1) simple phobia (N=27) 35.8 (21.1) normal control (N=46) 30.7 (19.4) Ehlers and Breuer (1992)study 3 panic disorder (N=13) 23.0 (22.2) PD and GAD both lower error scores than MD general. anx. dis. (n=15) 21.0 (13.8) major depression (N=16) 43.0 (21.9) Ehlers et al., (1995) panic disorder (N=112) 27.6 (21.6) PD lower error scores than NC normal control (N=40) 35.1 (25.0) panic disorder medicateda (N=24) 39.9 (29.8) unmedicated patients lower error scores unmedicated (N=107) 28.7 (21.7) panic disorder (N=40) pretreatment 27.9 (21.1) no difference pre–post posttreatment 32.0 (22.0) Antony et al. (1994) panic disorder (N=15) pretreatment 24.7 (13.5) no difference pre–post posttreatment 21.1 (11.7) Antony et al. (1995) panic disorder (N=20) preexercise 27.3 (16.6) no differences among groups; physical exercise improved accuracy in each group to an equal extent postexercise 21.9 (15.9) social phobia (N=20) preexercise 27.1 (16.8) postexercise 19.8 (13.1) normal control (N=20) preexercise 33.3 (16.7) postexercise 27.3 (16.6) Barsky et al. (1994) panic disorder (N=32) 28.2 (19.2) no differences among groups. palpitations, no PD (N=99) 24.5 (17.3) normal control (N=64) 27.2 (19.4) Van der Does et al. (1997) panic disorder (N=23) 30.3 (26.8) no differences among groups. major depression (N=16) 42.7 (22.4) normal control (N=21) 37.1 (22.9) Abbreviations: PD is panic disorder, GAD generalized anxiety disorder, MD major depression, NC normal controls. aTricyclic antidepressants, β-blockers or other anti-hypertensive medication. Table options Van der Does et al. (1997)argued that comparing mean error scores between groups may not be the best way of analyzing the findings. This has to do with the validity of the HBP task. Although the test–retest reliability of the test is adequate (Ehlers and Breuer, 1992; Van der Does et al., 1997), its validity is uncertain. Ehlers et al., (1995)found support for the validity in the fact that there is a significant correlation between stroke volume and test results (Schandry, Bestler, & Montoya, 1993). Furthermore, almost all participants count fewer beats than actually occur, which is a logical outcome if participants accurately count their heartbeats but miss a few. Third, the possibility that participants estimate the duration of the trials and then make an educated guess about the number of heartbeats has been ruled out in several studies (e.g. Ehlers and Breuer, 1992). However, time estimation is only one of several alternative explanations of HBP test performance. Furthermore, participants' self-reports after the test are contradictory to the second argument. Participants typically report not having missed a few beats, but instead having felt a regular rhythm somewhat slower than the actual rhythm ( Van der Does et al., 1997). This makes it uncertain whether the perceived rhythm has anything to do with actual heartbeats. If, hypothetically, PD patients feel more nervous during the test, they may expect and count a faster heartbeat rhythm than normals. They would then get lower error scores, just because almost all participants underestimate their HRs. Alternatively, the lower error scores of PD patients may be caused by a small number of patients who accurately perceive their heartbeats (i.e. who have a 0% error score). Van der Does et al. (1997)therefore looked at individual test performance to decide whether a participant is an accurate perceiver. While the mean error scores were not significantly different among groups, more panic patients (7/23) accurately perceived their HRs than depressed patients (0/16) or normals (2/21). The nine accurate perceivers had higher anxiety sensitivity scores than nonaccurate perceivers. Within the latter group, perceived HR was unrelated to actual HR, unrelated to cognitive scores, but significantly related to state anxiety. As noted above, the division of participants into accurately and nonaccurately perceiving groups was first used by Ehlers and Breuer (1992), who had also noted that the majority of PD patients were not totally accurate. In fact, the findings by Ehlers and Breuer and by Van der Does et al. (1997)are quite similar. There is a difference in interpretation that is based on the assessment of whether or not the HBP test is a valid measure of heart rhythm. If the test is valid, a division into accurate/nonaccurate creates artificial boundaries. Since Ehlers and Breuer (1992)regard the test as valid, in all subsequent publications (reviewed above) only the continuous measure (% error) was used. Van der Does et al. (1997)instead, found support for the position that the test is valid for only a small minority of participants, who accurately perceive their heart beats. Most of the remaining participants did come up with a heart beat count, but this was unrelated to actual heart beats. In other words, the division may not be artificial. However, these findings may be dependent on the relatively small sample that was used in that study. Therefore, the authors of the studies listed in Table 1 decided to collaborate in a reanalysis. The data of these studies were pooled and reanalyzed. The first question that was addressed was whether the main findings by Van der Does et al. (differences in anxiety sensitivity scores between accurate/nonaccurate perceiving subjects and correlation with state anxiety) replicate in a larger sample. A number of additional questions was addressed. Firstly, Antony et al. (1995)tested their participants both at rest and after a period of physical exercise, and found that exercise improved the mean accuracy scores in all groups. It would be interesting to know whether this was due to improvement in the ratio accurate/nonaccurate perceivers or to an increase in anxiety or arousal level in nonaccurate perceivers. Secondly, it would be interesting to see whether the confidence ratings, as used in several studies, are different for accurate and nonaccurate perceivers. Thirdly, Ehlers et al., (1995)used two types of instructions as well as a distraction procedure. Distraction had little influence on the percentage error scores, whereas strict instructions did have influence. It is unknown whether this also applies to the dichotomous scores. A final question concerned the effect of treatment on accuracy of HBP. On the basis of percentage error scores before and after treatment, it has been concluded that good HBP is a rather stable individual characteristic (Antony, Meadows, Brown, & Barlow, 1994; Ehlers et al., 1995).

(1) Accurate HBP is more prevalent among panic disorder patients than among healthy controls, depressed patients, patients with palpitations and individuals with infrequent panic attacks. No differences were found between panic disorder patients and patients with other anxiety disorders. (2) Accurate HBP is uncommon, even in patients with anxiety disorders. (3) Only very high HRs (>100 bpm) lead to an increase in accuracy, but even then for only half of the subjects. (4) Heart beat perception is influenced by distraction (tone pips), which is problematic for studies that measured HBP by presenting different rhythms. (5) Accurate perception is not stable before and after treatment; inaccurate perception is more stable. (6) It remains unclear whether perceived heart rate is correlated with anxiety in inaccurately perceiving participants.