Inappropriate Sinus Tachycardia (IST) In The Psychiatric Clinic

I don’t recall what I was researching the other day but I happened across a brief review paper on a subject I have been following for a while (2). That subject is inappropriate sinus tachycardia (IST). I posted recently about closely following the cardiac status of patients being seen by psychiatry both on the inpatient side and in the outpatient clinic. When that is done a significant portion of those patients will have tachycardia defined as heart rate of greater than 100 bpm. In some cases the heart rate ranges as high as 120 to 130 bpm.  Many of these patients are surprised to learn how high their heart rate is and what constitutes a normal heart rate. Others are very focused on the cardiac status and experience palpitations in periods of rapid accentuated heart rate. I commonly hear “it feels like my heart is coming out of my chest”.

That type of cardiac symptom can certainly occur during panic attacks. The majority of people I see with sinus tachycardia do not have panic attacks or panic disorder. They are generally anxious but the phenomenon I have not seen addressed is how much anxiety is due to the cardiac symptoms? Many have what I describe as cardiac awareness. By that I mean they can sense their heart beating by various mechanisms. Many can feel the pulsation of blood through the body especially in the head and neck area. Others can hear their heartbeat. Many can sense their heart beating against their chest wall. The person has that kind of focus any irregularity like occasional pauses or extra beats leads to heightened anxiety. As that anxiety builds some people will feel chest pain, chest pressure, and shortness of breath or near panic symptoms.

 A significant number of those patients will have anxiety associated with symptomatic IST. There are also groups of patients with frequent panic attacks, nocturnal panic attacks, night terrors, and medical problems associated with tachycardia and other cardiac symptoms.  It has been surprising to me to find that significant sustained sinus tachycardia is often ignored in primary care settings. The reason for that may be the latest review in UpToDate (1). In that review the authors define the syndrome and the evaluation and conclude that the condition generally has a benign course in that tachycardia induced cardiomyopathy is rare. They suggest that diurnal variation of the tachycardia may protect against that.

Since IST is by definition tachycardia with no known medical cause intrinsic heart disease and associated causes of tachycardia need to be ruled out. In psychiatric patients panic attacks and anxiety are typically considered psychiatric causes of tachycardia but they are rare causes of sustained tachycardia. The hyperadrenergic state of panic attacks generally resolves when the panic attack resolves and that is frequently in 20 minutes or less.  It is common to see very anxious people in clinics and when their vital signs are checked they are typically normal. Sustained tachycardia is more common with other comorbidities such as medication side effects, excessive caffeine use, stimulant use, alcohol or sedative hypnotic withdrawal, and in some cases insomnia. Deconditioning can also be a factor one person has been isolated and sedentary for any reason and they suddenly need to walk a distance to get to the clinic. There is a gray zone of overlapping conditions that need to be considered. For example, an acute pulmonary embolism, congestive heart failure, and emphysema or COPD can lead to cardiopulmonary symptoms including tachycardia. They can generally be ruled out by a medical history, review of systems, and brief examination.

Tachycardia secondary to medication side effects often requires tracking several variables.  In the ideal case, an indicated medication can be selected that does not have the side effect - in this case tachycardia. But there re some medications that are unique enough that they may be used in situations where the tachycardia persists because there are no other good alternatives. With clozapine (3) the tachycardia can be secondary to anticholinergic side effects, alpha blockade and hypotension, or intrinsic cardiac side effects like myocarditis. Patient often get tachyphylaxis to the anticholinergic effects but all of these variables need close monitoring. It takes a lot of ruling out to conclude that a patient on clozapine has IST and this is a good example of the importance of the baseline evaluation and reviewing avaiable records and vital signs in the electronic medical record.

A more common scenario is the anxious patient with no clear cardiac or pulmonary disease who has persistent tachycardia and in many cases palpitations. They are often treated with beta-blockers with some success. I have seen people have been unable to tolerate beta-blockers, people who did not respond beta-blockers, and some people with beta-blocker withdrawal who had severe anxiety panic and tachycardia because the beta-blocker was stopped too quickly. In both the review and the up-to-date summary, IST patients are commonly resistant to beta-blockers and need another intervention. The suggested intervention is ivabradine a novel medication described as a blocker of the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel responsible for the cardiac pacemaker I_f current. That directly affects heart rate at the SA node. It also affects retinal currents leading to phosphenes or transient bright spots in the visual fields. 

The main indication for ivabradine is congestive heart failure. There are cardiac complications including atrial fibrillation. That suggests to me that most psychiatrists should probably not consider prescribing this medication unless there is ample clinical experience and the required monitoring is not intensive - similar to beta-blockers today.

The main message in this post is that close attention does need to be paid to vital signs on every inpatient unit and outpatient psychiatric clinic. It is not enough to say that tachycardia can be dismissed as anxiety. It is also not enough to use a quasi-medical intervention like telling the patient to drink more fluids if they have not been assessed for hypovolemia. A close look for intrinsic cardiac conditions and the list of conditions and the differential diagnosis from the review article below and the UpToDate review should be a minimal requirement for medical psychiatrists. If that cannot be done, the patient should definitely see their primary care physician preferably prior to initiating any treatment with a medication that would obscure the clinical picture. The evaluation and recommendations of the primary care physician should be available in the patients psychiatric chart. For completion, I also get copies of other cardiac testing that has been done including echocardiograms and exercise stress tests.

The advantage of a diagnosis of IST is that it recognizes there is a specific diagnosis to account for inappropriate tachycardia rather than a default psychiatric diagnosis. That is important because it protects the patient and potentially offers more effective care. The treating psychiatrist should still be in the loop for the necessary lifestyle modifications, education about the condition and monitoring and treating any associated anxiety.

George Dawson, MD, DFAPA

References:

1.  Munther K Homoud. Sinus tachycardia: Evaluation and management.  Section Editor: Jonathan Piccini, MD, Deputy Editor:Brian C Downey, MD in UpToDate.  Accessed on October 6, 2019.

2.  Ruzieh M, Moustafa A, Sabbagh E, Karim MM, Karim S. Challenges in Treatment of Inappropriate Sinus Tachycardia. Curr Cardiol Rev. 2018 Mar 14;14(1):42-44. doi: 10.2174/1573403X13666171129183826. Review. PubMed PMID: 29189171; PubMed Central PMCID: PMC5872261

3. Miller DD. Review and management of clozapine side effects. J Clin Psychiatry.2000;61 Suppl 8:14-7; discussion 18-9. Review. PubMed PMID: 10811238.