Areas of Focus

Paroxysmal Supraventricular Tachycardia (PSVT)

PSVT is due to an abnormality in the electrical system of the heart. People with this condition have sudden and unexpected episodes of rapid heartbeat that start and stop without warning.

A normal resting heart rate is between 60 and 100 beats per minute. During a PSVT episode, a patients’ heart rate increases dramatically, sometimes exceeding 250 beats per minute. While experiencing an episode of PSVT, symptoms may include palpitations, sweating, chest pressure or pain, shortness of breath, sudden onset of fatigue, fainting, and anxiety. PSVT symptoms are commonly misdiagnosed as anxiety or panic attacks, especially in women.

PSVT episodes can first appear at any time in a patient’s life time and may occur in otherwise healthy patients. The frequency and severity of PSVT episodes vary from patient to patient and can even vary within an individual patient. Our market research shows patients living with PSVT experience a median of four to seven episodes per year despite up to two-thirds of them taking daily prescription medications to prevent episodes. These episodes may last anywhere from minutes to hours and can be debilitating for patients, leaving them unable to focus on family or work. Market research also shows that, in the year of diagnosis, almost 40% of PSVT patients experience multiple episodes per year that last more than 10 minutes, with 10% of episodes being reported as severe enough to warrant a trip to the hospital for treatment. After the first year of diagnosis, these percentages decrease modestly to approximately one-third of those surveyed, likely due to medication use and vagal maneuvers.

While PSVT is not typically life threatening, the uncertainty of when an episode will occur and how long it will last can significantly impact patient quality of life. Researchers have noted that up to 27% of patients living with PSVT stopped driving for fear of temporary loss of consciousness.

Prevalence and Incidence

PSVT affects approximately two million Americans and results in as many as 300,000 new diagnoses and over 600,000 healthcare claims in the United States per year, including emergency department visits, hospital admissions, and ablations. These estimates are based on an analysis of employer-based medical claims data for patients under age 65 and Medicare claims data for patients age 65 and older between 2008 and 2016.

Earlier published sources documenting the demographics, clinical characteristics, and epidemiology of PSVT relied on a single medical encounter confirmed by an ECG to estimate incidence and prevalence, and this may have significantly underestimated the prevalence due to the episodic nature of the disease, as well as the variability in the duration of episodes.

How common is PSVT in the USA? Milestone presented the answer at the 2018 International Academy of Cardiology’s Scientific Sessions.

Healthcare Economics

Current treatment for PSVT consumes significant healthcare resources. Our longitudinal analyses show mean annual costs per patient increase to approximately $30,000 in the year following diagnosis. Of note, catheter ablations only represent 23% of this increased spend. In addition, rates of emergency department visits and hospitalizations are 1.8 and 3.0 times higher, respectively, following diagnosis. In total, we estimate that approximately 80,000 catheter ablations and more than 150,000 ED visits/hospital admissions for PSVT occur each year, driving the majority of the approximately $3 billion spent annually in the United States on the management of PSVT.

How costly is PSVT to our health system? Milestone presented the answer at the 2018 International Academy of Cardiology’s Scientific Sessions.

Our Approach

We have designed and are developing the investigational drug, etripamil: a new, potent, and fast-acting calcium channel blocker in the form of a nasal spray to stop PSVT whenever and wherever it occurs.

The current standard of care for an episode of PSVT is an intravenous (IV) injection of adenosine, usually given in a hospital or emergency department. Adenosine blocks conduction over the atrioventricular (AV) node, a piece of electrical tissue in the heart, interrupting the arrhythmia and restoring a normal heart rate. In response to adenosine administration, patients may experience chest tightness, flushing, and even a sense of impending death. Adenosine is eliminated from the body in less than one minute and cannot be self-administered, as it requires IV access.

Prior to the approval of adenosine, PSVT was treated with IV calcium channel blockers, such as verapamil or diltiazem, that also slow conduction over the AV node within minutes. These drugs bear risk of excessive slowing of the heart and low blood pressure. In-hospital IV administrations are associated with higher healthcare costs and are unsettling and inconvenient for the patient.

Many patients take daily oral medications, such as beta blockers, calcium channel blockers or antiarrhythmic drugs in an attempt to prevent or control the frequency and duration of future PSVT episodes. Even so, “breakthrough” episodes requiring visits to the emergency department may occur. Some patients may discontinue oral medication due to intolerable side effects. For instance, taking beta blockers chronically may cause sexual dysfunction or fatigue, and long-term use of verapamil may cause constipation

The only potentially curative treatment for PSVT is ablation, an invasive interventional procedure, which cauterizes the short circuit that is the cause of the abnormal rhythm. This procedure burns or freezes the heart’s abnormal electrical tissue with catheters that are run through the patient’s groin vessels and into the heart. Analyses of insurance claims suggest less than 10% of patients living with PSVT annually resort to this.

Clinical Trials

Milestone is the only company actively conducting phase 3 trials for any therapeutic intended to treat PSVT.

The PSVT Place Registry

There is limited published research characterizing the burden that PSVT places on patients, especially from their perspective. Basic questions about episodes, such as the frequency, duration, severity, and physical/emotional consequences, need further data to be better understood. For this reason, Milestone is sponsoring The PSVT Place Registry so that patients have the opportunity to provide their first-hand experience. Our goal is for this database to allow researchers to study the condition from the patient perspective and share aggregate data back with the patient community via reports and publications. The more medical (or health) information is gathered from the community, the more clarity we can bring to this condition, together. If you have PSVT, please consider joining today.

Let’s Work Together

We collaborate with leading researchers, academic institutions, scientific societies, patient support organizations, and others who are like-minded in the pursuit of PSVT knowledge and education. If you are interested in collaborating, please email