Psychiatrists have long observed that a significant number of patients who present with cardiac symptoms to nonpsychiatric physicians are actually suffering from panic disorder, but a new analysis of some old data shows that a small subset of patients diagnosed with panic disorder may actually be suffering from a minor heart ailment.

A retrospective study in the March 10 issue of the Archives of Internal Medicine found that in more than half of 107 patients, paroxysmal supraventricular tachycardia (PSVT) was unrecognized after initial evaluation and remained unrecognized for an average of three years and four months.

Prior to eventual diagnosis of PSVT, physicians, all nonpsychiatrists, attributed symptoms to panic attacks, anxiety, or stress in 54 percent of 59 patients who underwent an initial medical evaluation. Twelve percent of the patients with initially recognized PSVT sought psychiatric care or counseling specifically for symptoms later found due to PSVT.

DSM-IV cites supraventricular tachycardia along with other medical conditions in the differential diagnosis of panic disorder, the authors note. But prior studies have not specifically documented "the extensive overlap of symptoms between panic disorder and PSVT, with clear demonstration of erroneous attribution of PSVT symptoms to psychiatric cause," they write.

The study revealed a strong gender bias in that unrecognized PSVT was attributed to psychiatric causes in women twice as often as in men.

One major limitation of the study is that it was done retrospectively, relying on patients' recollections of dates, symptoms, and knowledge of events from several years earlier, the authors note.

The findings are intriguing for both psychiatrists and nonpsychiatric physicians, but their clinical significance should not be exaggerated, according to James Ballenger, M.D., professor and chair of the department of psychiatry at the Medical University of South Carolina in Charleston.

Ballenger, who has studied panic disorder for 25 years, believes the findings could cause undue anxiety in patients already prone to anxiety. Despite the findings, he believes that there are far more patients who are incorrectly diagnosed with cardiac disease when they are actually suffering from panic disorder than the other way around.

"This is a potentially important article in that it may uncover some new ideas in the panic disorder field and a new way of approaching [what is] probably a small subset of patients. Its other importance is [that] it might lead to a lot of anxiety, confusion, and even chaos in the field if the implications are not carefully thought through. I have already had patients call who were made anxious by seeing a reference to this study on television."

The "simplest way" of thinking about the study is "probably wrong," Ballenger said. That would be "to think that for the majority of panic disorder patients there is an etiology that has been overlooked." But the findings are worth pursuing and "clearly need to be researched well and soon," he added.

For patients with panic disorder, and clinicians who treat them, Ballenger cautioned, "The crux of the issue probably is that the number of patients who have PSVT is small, certainly in relation to the number of people with panic disorder."

In the study, the authors cite the psychiatric literature--correctly, according to Ballenger--as having found little in the way of cardiac abnormalities in panic disorder. "What we routinely find is sinus tachycardia," said Ballenger. "And that should be fairly easily distinguishable from PSVT."

Sinus tachycardia may be indicative of stress, anxiety, physical exertion, or other events but is not indicative of cardiac pathology.

PSVT is "not something that the average panic patient" should be concerned about, Ballenger said. He noted that the cost of a cardiological workup to rule out the condition completely could run as high as $1,500, and "it would not be necessary or valuable in the overwhelming number of patients who have panic disorder."

There needs to be a study of at least 100 patients diagnosed with panic disorder to see how many have PSVT, said Ballenger.

"It would be interesting to have a group of patients who because of a small, aberrant piece of tissue in their hearts have runs of severe tachycardia, shortness of breath, and sweating"--all typical symptoms of a panic attack, said Ballenger. "It would be interesting to see if that could lead to panic disorder. That would tell us something about panic disorder in general."

The study's lead and senior authors, Timothy Lessmeier, M.D., and Michael Lehmann, M.D., discussed their findings with Psychiatric News. Both are cardiologists who specialize in electrophysiology. Lessmeier now works with the independent Heart Clinics Northwest of Spokane, Wash. Lehmann is a clinical associate professor of medicine at Wayne State University and director of the Arrhythmia Center at Sinai Hospital in Detroit.

For both psychiatrists and nonpsychiatric physicians, PSVT represents a small but real liability risk, since the disorder carries some potential for causing sudden death, they commented. PSVT is readily treatable with a success rate of more than 90 percent with a procedure called radiofrequency ablation.

Radiofrequency ablation removes the underlying cause of the disorder--excess conductive tissue--by destroying it with high-frequency radio waves administered to a specific site through the tip of a catheter. Left intact, the extra conductive tissue triggers episodes of rapid heartbeat by sending electrical impulses that override the heart's normal pacemaker.

Lehmann likened it to having an extra "electrical cable" capable of conducting impulses. In the normal conducting system they go from upper to lower chamber (sinus node to ventricles) but with the extra impulse they can return back up to the atria, triggering the tachycardia.

All the misdiagnoses identified in the retrospective analysis were made by nonpsychiatric physicians, "whether internists, primary care physicians, or cardiac doctors. . . . It's nonpsychiatrists who are jumping to the conclusion that it's just an anxious person," Lehmann observed.

Lehmann said he hoped the study would lead to "a more interdisciplinary approach among psychiatrists, cardiologists, and internists to better understand the nature of the diagnostic confusion and overlap between panic syndromes and PSVT."

This study started with PSVT, he pointed out. "Now we need to look at the panic-disorder population to determine the extent to which these patients may actually be suffering from PSVT."

The original data were gathered from April 1991 to May 1993 as part of an electrophysiological study. The retrospective analysis was conducted from 1993 through 1995. When the team, then at Wayne State University, spoke to psychiatrists about the confusion of PSVT with panic disorder, the psychiatrists told them that they assumed that cardiovascular disorders had already been ruled out by the time a patient was referred to them for psychiatric treatment.

"The irony is you have nonpsychiatrists making a psychiatric diagnosis," said Lehmann. "And then you have the psychiatrists assuming [the nonpsychiatrists] did their homework in excluding cardiologic conditions. So that means that the psychiatrists need to be a little more wary of the psychiatric diagnosis."

What should primary care physicians and psychiatrists take away from this? Said Lessmeier, "It isn't that every patient should have [a cardiac] event monitor. What we think is important is that if you have a patient with panic attacks in whom [heart] palpitations are prominent, this diagnosis ought to be considered."

(Psychiatric News, April 4, 1997)