Inappropriate sinus tachycardia – Elevated heart rate and the vagus nerve

Ross Hauser, MD

Inappropriate sinus tachycardia and postural tachycardia syndrome (POTS) are very similar problems that cause an elevated heart rate. While they share common cardiovascular-like symptoms, there is the main difference that separates their diagnosis.  POTS and its cardiovascular-type symptoms are triggered by a change in body position or orthostatic stress, such as when you get up from bed or go from a reclining to a standing position. Inappropriate sinus tachycardia is a condition where the heart races and there is no understandable reason for it other than it is “inappropriate.”

In some people, both diagnoses can be made simultaneously. Inappropriate sinus tachycardia and postural tachycardia syndrome can be seen as concurrent problems as opposed to a “this or that” diagnosis.” Further compounding this concurrent diagnosis is the equally confounding diagnosis of bradycardia. Your heart rate has become too slow. Such is the complexity of heart rate for some people.

This article is a companion article. For more comprehensive information I invite you to also read my article: Can cervical spine instability cause cardiovascular-like attacks, heart palpitations, and blood pressure problems?

What are we discussing in this article?

  • Why do most inappropriate sinus tachycardia treatments fail?
  • Sinus node modification.
  • Eventually, your heart says enough is enough and you go from a heartbeat that is too fast to a heartbeat that is too slow.
  • How do you go from a fast heartbeat to a slow heartbeat? Medication and the heart try to reboot itself.
  • A review of Inappropriate sinus tachycardia – “depressed efferent parasympathetic/vagal function.”
  • Heart thickening, treatment failure, is the treatment answer for some in Vagus nerve dysfunction?
  • Is the Vagus Nerve a path of diagnosis and treatment?
  • Dizziness, balance problems, and blood pressure swings can be from upper cervical instability.
  • Postural Orthostatic Tachycardia Syndrome (POTS) – how cervical instability affects the heart.
  • Autonomic nervous system (ANS) regulation and Heart Rate and Heart Rate Variability – Is this the answer for some?
  • The main highway of heart-to-brain communication via the autonomic nervous system is the vagus nerve.
  • The idea that upper cervical spine instability impacts heart rate and heart rate variability and this may be a culprit of your symptoms, is not a new idea.

In this article I will present one possible cause of inappropriate sinus tachycardia, that is upper cervical instability.

Inappropriate sinus tachycardia treatment failures. Research: “Among all medical therapies, there were high rates of treatment failure or symptom worsening in over three-quarters of patients in our study.

As you are reading this article it is very likely that you are searching for answers to why your inappropriate sinus tachycardia or POTS is difficult to treat. An April 2021 paper published in the Journal of Cardiovascular Electrophysiology (1) starts with the acknowledgment that “Effective therapy for inappropriate sinus tachycardia remains challenging with high rates of treatment failure and symptom recurrence. It is uncertain how effective pharmacotherapy and procedural therapy are long-term, with poor response to medical therapy in general.”

The purpose of this study was to try to assess what conventional medicine treatments for inappropriate sinus tachycardia may work and those that may not work. To do this they started off with 305 patients with a formal diagnosis of inappropriate sinus tachycardia.

  • 259 (84.9%) receive at least one prescription medication related to the condition.
    • Beta-blockers were the most commonly used medication, with a majority of patients reporting no change or worsening of symptoms, and the poor response was seen to other medication classes.
    • Improvement was seen significantly more often with ivabradine (Procoralan – (hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blockers) ) than beta-blockers, though the study size was very limited.
    • Fifty-five patients (18.0% of all inappropriate sinus tachycardia patients), average age 32 years old, underwent a sinus node modification (some will eventually get a pacemaker – explained below) procedure, with an average of almost two procedures needed per patient.  Acute symptomatic improvement (of less than 6 months) was seen in 58.2% of patients.
    • Long-term complete resolution of symptoms was seen in 5.5% of patients, modest improvement in 29.1%, and no long-term benefit was seen in 65.5% of patients.

The researchers of this study concluded: “Among all medical therapies, there were high rates of treatment failure or symptom worsening in over three-quarters of patients in our study. Ivabradine was most beneficial, though the sample size was small. While most patients receiving sinus node modification ablation for Inappropriate sinus tachycardia perceive an acute symptomatic improvement, almost two-thirds of patients have no long-term improvement, and resolution of symptoms is quite rare. AV node ablation with pacemaker implantation following lack of response to sinus node modification offered increased success, though the sample size was limited.”

A November 2022 paper in the American journal of cardiology (6)  describes the pharmacological treatment of inappropriate sinus tachycardia. Some of the learning points of this paper include a further discussion on :

  • “Pharmacological treatment of inappropriate sinus tachycardia aims to reduce heart rate and symptoms but has relatively low success.”
  • Long-acting beta blockers are used as first-line therapy.  . . However, dosing is of paramount importance to avoid excessive bradycardia during sleep and hypotension.
  • Ivabradine has been shown to be effective in treating inappropriate sinus tachycardia with good tolerance. However, ivabradine is not effective in symptom control of inappropriate sinus tachycardia in up to 30% of patients.

Why do most inappropriate sinus tachycardia treatments fail?

Let’s go back to a 2001 study in the journal Pacing and Clinical Electrophysiology. (2) The purpose of going back more than twenty years is to show how two decades’ worth of research and betterment of technology still leads us with the same questions these doctors had in 2001. Why inappropriate sinus tachycardia standard of treatment does not help and may have made things worse for some people. The 2001 study comes to us from the Division of Cardiovascular Diseases and Internal Medicine, Mayo Clinic, and Mayo Foundation.

“Inappropriate sinus tachycardia and postural orthostatic tachycardia are ill-defined syndromes with overlapping features. Although sinus node modification has been reported to effectively slow the sinus rate, the long-term clinical response has not been adequately assessed. Furthermore, whether patients with postural orthostatic tachycardia would benefit from sinus node modification is unknown.”

Some of you reading this article may have had sinus node modification.

Some of you reading this article may have had sinus node modification. This was either the use of medications to slow your heart rate, lifestyle changes, and for some, eventually the need for atrioventricular or AV node ablation. In this procedure radiofrequency is used to burn off a small amount of heart tissue. Then a pacemaker will be installed. It is considered the standard of care as previously mentioned, medication for inappropriate sinus tachycardia has not been shown effective in the long term.

In this 2001 study, some observations were made that describes patients who effectively had their heart rate slowed but still had symptoms consistent with postural orthostatic tachycardia syndrome and inappropriate sinus tachycardia…

  • Seven female patients average age 41.
  • 5 of the 7 (71%) patients had successful sinus node modification.
  • Despite the significant reduction in heart rate, clinical symptoms were not significantly improved after sinus node modification in patients with inappropriate sinus tachycardia and postural orthostatic tachycardia. A primary subtle autonomic dysregulation is frequently present in this population. Sinus node modification is not recommended in this patient population.

So what is being suggested? Sinus node modification, medications, or pacemakers may not be recommended for some people because the issue these people have is something else. It can be autonomic dysregulation. This is why people who are being treated for rapid heartbeat can have their heartbeat regulated but they continue to have symptoms of shortness of breath, dizziness, fainting sensation or actually fainting, panic attacks, anxiety attacks, and other psychological-like problems.

Eventually, your heart says enough is enough and you go from a heartbeat that is too fast to a heartbeat that is too slow.

A May 2021 paper in The Journal of Innovations in Cardiac Rhythm Management (3) comes to us from the Division of Cardiovascular Medicine, Department of Medicine, University of Toledo. Here the discussion centers on that not only can inappropriate sinus tachycardia and postural tachycardia syndrome lead to a rapid heart rate and exist as concurrent diagnosis, but a third entity can develop, “sustained symptomatic bradycardia” or a heart rate that slows down too much.

Let’s look at the summary highlights of this paper which describes patient case histories of people with a heart rate that is out of cardiac rhythm and the symptoms it caused them. (The parenthesis are added as explanatory notes).

“Distinguishing POTS from similar syndromes depends on adherence to specific clinical criteria, with the differential including inappropriate sinus tachycardia, chronic fatigue syndrome, pheochromocytoma (tumors on the adrenal glands), and neurocardiogenic syncope (This is a situation where you may faint at the sight of blood or other stimulation. This is the result of an overreaction and over response of the vagus nerve – the vagus nerve is discussed below).

Specifically, inappropriate sinus tachycardia has overlapping features with POTS, which can make proper diagnosis a nebulous task as both disorders result in an increase in heart rate with minimal activity.

However, POTS is usually associated with elevations in heart rate in response to changes in the body position, whereas this is possible but not essential to make a diagnosis of inappropriate sinus tachycardia.”

Let’s stop here for a brief recap.

Many people with these problems, likely including yourself as you read this article, have been on a long medical journal trying to figure out why your heart rhythm fluctuates. Your story may sound very familiar to these types of problems people write to us about:

  • No real diagnosis.
  • Debilitating heart palpitations with no known cause. Their doctors are at a loss to understand their problems.
  • Tachycardia for no reason that comes on suddenly and goes just as quickly (it is at this time a person will receive a diagnosis of Inappropriate sinus tachycardia).
  • Doctors express concern that they may be suffering from psychological symptoms with the hopes that they can offer medication for the panic attacks, anxiety, stress, and depression the person may suffer from.
  • Patients express concern that they do not have psychological symptoms, that their inappropriate heart racing triggers their panic attacks, and not the other way around.
  • Chronic and disabling dizziness, faint feeling standing or sitting.
  • Cardiovascular testing, including heart monitors and repeated EKGs, and other tests can not pinpoint anything.
  • Over time your heart slowed itself down. It slowed itself down too much.

How do you go from a fast heartbeat to a slow heartbeat? Medication and the heart try to reboot itself.

Sick sinus syndrome is the inability of the heart’s natural pacemaker (sinus node) to create a heart rate that’s appropriate for whatever activity or rest you are doing at the moment. It causes irregular heart rhythms (arrhythmias). Sick sinus syndrome is also diagnosed as sinus node dysfunction or sinus node disease.

When the heart rate is in dysfunction and has continuous rapid heart rate, the heart may try to remodel itself by enlarging and thickening.

In the above study, the researchers wrote:

“As a rare but recurrent phenomenon, it has been observed in our clinic that patients suffering from POTS as well as inappropriate sinus tachycardia have an increased propensity for progression into sinus node dysfunction (the heart’s inability to create a natural pace or regulate its own natural pacemaker) consisting of episodes of either transient or sustained symptomatic bradycardia (low heart rate). We suspect the mechanisms of degeneration of the sinus node may be similar to those seen with other tachycardic dysrhythmias, such as atrial fibrillation or atrial flutter.”

In other words, the researchers suggested the slow heart rate came from the heart’s reaction to the fast heart rate and then created the thickening of the heart to slow things down.

December 2021: A review of Inappropriate sinus tachycardia – “depressed efferent parasympathetic/vagal function”

In the next sections, I am going to talk about the vagus nerve or as the next study presents it: “depressed efferent parasympathetic/vagal function.” Is the treatment answer for some in Vagus nerve dysfunction?

Specialists and cardiologists from the Department of Cardiology, Khyber Medical Institute in India, Walter Reed Medical Center, in Bethesda, the Department of Internal Medicine, Central Michigan University, Division of Cardiology, University of Toledo, and McLaren Greater Lansing Hospital in Michigan, combined research to discuss the various conditions, symptoms, and treatments linked to Inappropriate sinus tachycardia. Here is what they wrote, in December 2021 in the journal Reviews in Cardiovascular Medicine (4) parenthesis have been added as a means of layperson explanatory notes:

“Inappropriate sinus tachycardia has been defined as a resting heart rate of more than 100 beats per minute and an average 24-hour heart rate of more than 90 beats per minute with distressing symptoms resulting from the persistent tachycardia.

Possible mechanisms of inappropriate sinus tachycardia include:”

  • intrinsic sinus node abnormality, (sometimes referred to as sick sinus syndrome) this is the inability of the heart to maintain a natural pace or pacemaker abilities),
  • beta-adrenergic receptor stimulating autoantibody, (an autoimmune type disorder where beta-adrenergic receptor cells are attacked by the immune system),
  • beta-adrenergic receptor super-sensitivity, (an autoimmune type disorder where beta-adrenergic receptor cells are attacked by the immune system),
  • muscarinic receptor autoantibody or hyposensitivity, (muscarinic receptors slow the heart rate, if they are attacked by immune cells they do not slow the heart down),
  • impaired baroreflex control (the afferent baroreceptive nerves or their central nerve connections become impaired and this impacts pace and heart rate),”

The researchers also point out these conditions: They are explained at length below:

  • depressed efferent parasympathetic/vagal function (the possibility that you are in a constant state of stress caused by dysfunction of the parasympathetic nervous system by way of vagus nerve dysfunction.
  • nociceptive stimulation (Simply in this context nerve inflammation or dysfunction of pain receptors that can lead to stress, more specifically oxidative stress),
  • central autonomic overactivity (Dysfunction of the autonomic nervous system which can lead to chronic heart failure and hypertension),
  • aberrant neurohumoral modulation (neurohumoral modulation keeps the heart at balance and pace. When aberrant neurohumoral modulation occurs, this balance is upended and the heart can chronically race).

The paper also points out that despite symptoms associated with Inappropriate sinus tachycardia are palpitations, chest pain, fatigue, shortness of breath, presyncope, and syncope, Inappropriate sinus tachycardia has not been associated with tachycardia-associated cardiomyopathy or increased major cardiovascular events.

Then is it a heart problem, a neck problem, a vagus nerve problem? The answer can be yes to all.

What are we seeing in this image?

This is a simple diagram of a complex upper cervical vertebrae – vagus nerve – baroreceptor connection. The vagus, along with the glossopharyngeal nerve, run just in front of the upper cervical vertebrae (atlas and axis) and branch out to innervate (sends and receives nerve signals) the receptors in the carotid sinus and aortic arch that control blood pressure. When atlanto-axial instability is present, blood pressure issues (along with heart rate and rhythm problems) can occur because of impairment in vagus and glossopharyngeal nerve function.

Heart thickening, treatment failure, is the treatment answer for some in Vagus nerve dysfunction?

It is possible in some patients that cervical instability and degenerative disc disease, are contributing to a problem of autonomic myopathy or autonomic neuropathy. Terms that describe nerve damage that blocks or interferes with the messages sent between the brain and the heart and blood vessels. Diagnoses such as myocardial ischemia, angina, atrial fibrillation, ventricular tachycardia, mitral valve prolapse, postural orthostatic tachycardia syndrome (POTS), Inappropriate sinus tachycardia, drop attacks, and life-threatening hypotensive episodes can be from autonomic failure which can have a cervical structural etiology.

I am going to start building up evidence that blood blockage and vagus nerve dysfunction can be primary causes of Inappropriate sinus tachycardia in some people.

Let’s look at an October 2019 paper in the journal Frontiers in Cardiovascular Medicine (5). This paper, led by Lund University researchers in Sweden, wanted to assess the continued problems of syncope and orthostatic intolerance in paced (pacemaker) patients and why they continue to “constitute a common clinical dilemma.”

In this study:

  • 39 patients (average age of about 65 and 39% women) had a cardiac implantable electronic device (CIED).
  • The cause of their heart rate problems was traced to Orthostatic hypotension (41%) and vasovagal syncope (31%) were the most common diagnosis.

Explanatory note: Vasovagal syncope is a common form of fainting. It is usually attributed to standing too long, dehydration, excessive heat and is considered a transient event. You faint because something prevented you from getting enough blood to the brain. In this article, I will suggest that for some people, this blood blockage to the brain is being caused by compression on the nerves, arteries, and veins that pass through the neck.

What could it be? The pacemaker did not fail.

  • Returning to the current study – There were no cases of pacemaker dysfunction.
    • The original packing indications followed guidelines (the people had a pacemaker inserted based on current treatment guidelines: In this study of 39 patients the breakdown was:
      • sick-sinus-syndrome in 16
      • atrioventricular block in 16
      • atrial fibrillation with bradycardia in five.
    • Twenty-two of the 39 patients (56%) had experienced syncope prior to the original pacemaker implantation.
      • Orthostatic hypotension was diagnosed in seven (32%) and vasovagal syncope in nine (41%) of these patients.
      • Of the 17 patients that had not experienced syncope prior to the original pacemaker implantation, nine patients (53%) were diagnosed with orthostatic hypotension and vasovagal syncope was diagnosed in three (18%).
      • Of the 39 patients, two had implantable cardioverter-defibrillators to treat malignant ventricular arrhythmias diagnosed after syncopal episodes.
  • Conclusion: “Cardiovascular autonomic tests reveal the etiology of syncope and/or orthostatic intolerance in the majority of paced patients. The most common diagnosis was orthostatic hypotension (40%) followed by vasovagal syncope (30%), whereas there were no cases of pacemaker dysfunction. Our results emphasize the importance of a complete diagnostic work-up, including cardiovascular autonomic tests, in paced patients that present with syncope and/or orthostatic intolerance.”

Is the Vagus Nerve a path of diagnosis and treatment? What are we seeing in this image?

Here we see the “normal sequence of events” of how messages go from your brain through the vagus nerve to the heart. The messages between brain and heart are simple adjustments to maintain heart rate. Once the message is received the heart sends a message back to the brain via the glossopharyngeal nerve and the vagus nerve on heart rate and blood pressure.

Dizziness, balance problems, and blood pressure swings can be from upper cervical instability

Let’s stop here to explain some points. Ross Hauser, MD explains cases where otherwise unexplained dizziness, balance problems, blood pressure drops, and heart arrhythmias can have a structural cause – upper cervical instability.

Summary learning points of this video

  • There are a lot of people who have unexplained dizziness, balance problems, blood pressure swings, arrhythmia, palpitations, OR their heart rate can go really low.
  • They go to a cardiologist or several cardiologists and other doctors and no one seems to know the cause of their heart problems are.
  • We find that in a lot of these cases, the person is suffering from cervical instability especially upper cervical instability.
  • The sensory nerves that tell the brain what’s going on, moment to moment, in regard to heart rate and blood pressure are carried by the vagus nerve and the glossopharyngeal nerve. If the messages that these sensory nerves need to deliver to the brain are blocked or impaired, the heart symptoms described can develop.

Inappropriate sinus tachycardia – how cervical instability affects the heart

One of the most common questions we are asked is about POTS and Inappropriate sinus tachycardia are concerning the various and scary symptoms related to dysautonomia.

  • Dysautonomia –  problems of or dysfunction of the autonomic nervous system. Its symptoms such as lightheadedness, palpitations, and tremulousness during standing.

In this video, Ross Hauser, MD highlights some of the most common reasons why cervical instability or cervical dysstructure (broken neck syndrome) can be the underlying structural cause of low vagal tone and associated poor heart function, leading to POTS, Inappropriate sinus tachycardia, or dysautonomia. He also interviews a patient and nurse, Linda, about her experience being treated with Prolotherapy for POTS, nausea, and other neck instability symptoms.

For a more detailed discussion – please see my articles:

Can cervical spine instability cause cardiovascular-like attacks via autonomic dysregulation? Autonomic nervous system (ANS) regulation and Heart Rate and Heart Rate Variability – Is this the answer for some?

  • Heart Rate measures the number of heartbeats per minute.
  • Heart Rate Variability measures the time between individual heartbeats. Please see our article on Heart Rate Variability.

To understand what may be happening in these people we need to understand the autonomic nervous system. By itself, without conscious instruction, the autonomic nervous system keeps your heart pumping, your blood flowing through your blood vessels, and a myriad of other activities that occur in your body. Part of that myriad of duties includes the operation of the sympathetic nervous system and parasympathetic nervous system.

The main highway of heart to brain communication via the autonomic nervous system is the vagus nerve

  • The sympathetic nervous system is part of the autonomic nervous system. It helps make adaptations to your current situation. For instance, if you are witness to a crime or an accident, or something bad,  your body shifts into “fight-or-flight mode.” Your heart rate, blood pressure, and breathing rate dramatically increase.
  • The parasympathetic nervous system is an energy management center. When you are done being in “fight or flight mode,” or are using techniques to end a panic attack to catch your breath or calm yourself down. The parasympathetic nervous system helps automatically reduce heart rate and blood pressure. As opposed to “fight or flight,” the parasympathetic nervous system is often described as “rest and digest,” as it signals to send blood back into the gut and digestive system.

So here we have the autonomic nervous system and its components, the sympathetic nervous system and parasympathetic nervous system, that among its duties regulate your heart rate. Its main highway of communication is the vagus nerve of which there are two running down each side of the neck. The vagus nerve has a great impact on heart function, as the cardiovascular afferents (afferents – simply the nerve fibers that send messages to the brain as opposed to efferents, nerve fibers which send the response back) make up the greatest extent (compared to other organs) of the 85-90% of sensory fibers which make up the vagus nerve.

In other words, the majority of work the vagus nerve does is getting messages back and forth from brain to heart. These afferents (messages in) go through the nodose ganglion (nerve bundle) which sits in front of the atlas (C1 vertebra). If the C1 vertebra is unstable and causes problems of “nerve pinching” this is how upper cervical instability can affect the heart rate variability.

What are we seeing in this image? This is a good summary of the vagus nerve and the glossopharyngeal nerve monitoring the blood pressure and pulse in the body.

The afferent information, that is messages from the cardiovascular system, in this case, the baroreceptors that send messages on blood pressure to the brain is relayed through the nucleus tractus solitarius. The nucleus tractus solitarius is a nervous system relay station that receives and responds to various messages including those of blood pressure levels and the medulla sends messages back to the cardiovascular system about what to do with these blood pressure levels.). If the signals to the brain that the heart is racing or blood pressure is elevated are not correctly received, the correct message back to slow the heart rate down is never sent.

The idea that upper cervical spine instability impacts heart rate and heart rate variability and this may be a culprit of your symptoms, is not a new idea.

The idea that upper cervical spine instability impacts heart rate variability and this may be a culprit of your symptoms, is not a new idea. In our 28 years of helping patients with problems related to the cervical spine, we have seen these symptoms many times. Yet medical research is not yet that abundant. In our own peer-reviewed published studies we have been able to document cervical neck ligament damage as a possible cause of low HRV as to when cervical neck ligaments are damaged or weakened by wear and tear damage or injury, they allow the upper cervical instability that can impinge on the cervical nerves.

Summary and contact us. Can we help you? How do I know if I’m a good candidate?

We hope you found this article informative and it helped answer many of the questions you may have surrounding Inappropriate sinus tachycardia. Just like you, we want to make sure you are a good fit for our clinic prior to accepting your case. While our mission is to help as many people with chronic pain as we can, sadly, we cannot accept all cases. We have a multi-step process so our team can really get to know you and your case to ensure that it sounds like you are a good fit for the unique testing and treatments that we offer here.

Please visit the Hauser Neck Center Patient Candidate Form

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References:

1 Shabtaie SA, Witt CM, Asirvatham SJ. Efficacy of medical and ablation therapy for inappropriate sinus tachycardia: A single‐center experience. Journal of cardiovascular electrophysiology. 2021 Apr;32(4):1053-61. [Google Scholar]
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5 Yasa E, Ricci F, Holm H, Persson T, Melander O, Sutton R, Fedorowski A, Hamrefors V. Cardiovascular autonomic dysfunction is the most common cause of syncope in paced patients. Frontiers in cardiovascular medicine. 2019 Oct 25;6:154. [Google Scholar]
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This article was updated January 9, 2023

 

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