Below, please find links to all of the clinical trials involving cardiology. The studies include a multitude of information, including (but not limited to) the study’s purpose, benefits for participating, and financial incentive information. If you have any questions, please contact the individual outlined at the end of each trial summary.

Please visit the Cardiology service webpage at the Veterinary Medical Teaching Hospital (VMTH) if you would like to learn more about the amazing things that our veterinarians can do for you and your animal.

Horses & Ponies

Ventricular Septal Defects in Arabian Horses: Identifying the Genetics

Title: Equine Ventricular Septal Defects

Purpose of Study: Ventricular Septal Defects (VSDs) are the most common congenital heart defects in horses. They allow blood to shunt inappropriately from the left ventricle to the right ventricle via an opening in the ventricular septum. This blood recirculates through the lungs and left chambers, resulting in enlargement of these structures. Arabian horses are overrepresented in horses presenting for VSDs, and we are investigating the possibility of a genetic predisposition for this defect.

Contact: Eric Ontiveros, Stern Laboratory Coordinator: ( or 530-752-4892)

Participation Requirements: Arabian horses or Arabian crosses that have a right-sided systolic heart murmur, or a veterinary diagnosis of VSD. Horses must tolerate handling and stand for the echocardiogram.

Initial Evaluation for Participation: None.


  • Collection and submission of a blood sample (3ml in an EDTA purple top) for DNA extraction by the cardiac genetics laboratory


  • Results from this study will determine if a genetic factor plays a role in the development of Ventricular Septal Defects in Arabian horses. This finding would have great significance regarding screening predisposed horses and hopefully guiding breeding management to avoid continuation of this defect in the Arabian horse.

Owner Responsibilities:

  • Submission of a blood sample either by the owner or referring veterinarian
  • If your Arabian was diagnosed with a heart murmur but you are unsure whether it qualifies for the study, please contact us. In some cases, we may be able to review your horse's medical records or even fund a cardiac examination for your horse.

Printable Flyer (PDF)


Abnormal/Rapid Heartbeat (Ventricular Arrhythmia): Assessing Treatment

Title: Acute effects of sotalol on echocardiographic indices of ventricular function in dogs with ventricular tachyarrhythmias

Purpose: Sotalol is considered by most veterinary cardiologists to be one of the most effective and well-tolerated medications for longterm control of potentially life-threatening ventricular arrhythmias (abnormal and rapid heartbeats arising from the pumping chambers). Sotalol may decrease heart function (pumping ability) but it is currently unknown to what extent, if any, it does so. Therefore, the purpose of this clinical trial is to determine the effect of a single standard dose of sotalol on heart function and rhythm in dogs diagnosed with ventricular arrhythmias.

Contact: For questions or any research-related injuries or adverse events, please contact the Principal Investigator, Dr. Lance C. Visser, DVM, MS, DACVIM (Cardiology) at (616) 633-6231 or To schedule an appointment, please contact Pam McInnis at

Participation Requirements: Dogs that have been diagnosed with a ventricular arrhythmia (abnormal and rapid heartbeats originating in the pumping chambers of the heart)

Initial Evaluation for Participation:  Dogs should be evaluated for the presence of ventricular tachyarrhythmias by a veterinarian. Dogs will be considered ineligible for the study if they weigh less than 10 kg (20 lbs), are already taking sotalol, are taking heart medications that affect heart function (e.g., pimobendan or beta-blockers), and if they are affected with significant kidney disease.

Procedures: Please note that no diagnostic test or therapeutic intervention will be withheld or delayed for any reason for the purposes of this study and no “experimental” tests or drugs will be used in this study.

If you agree to let your dog participate in this study, the following will happen:

  • Review of your dog’s medical history, medication history, and any clinical signs (symptoms) your dog may be experiencing with your dog’s attending clinician
  • Completion of a physical examination with particular attention paid to the cardiovascular system
  • Complete echocardiogram (cardiac ultrasound) without the use sedatives. Echocardiograms involve your dog being gently restrained while lying on their side and usually last 20-25 minutes.
  • Immediately following this echocardiogram, your dog will be administered a single standard dose (2 mg/kg) of sotalol by mouth after which your dog will be monitored in the cardiology service room or patient care ward by direct observation.
  • 2-4 hours after your dog received the sotalol medication (allows time for the drug to take effect), your dog will have the exact same echocardiogram performed, after which your dog’s participation in the clinical trial will be completed.
  • Blood collection (2 mL) to look for genetic mutations that may cause a lack of response to the drug.

It is important to understand that this study is not a therapeutic trial; it is a study assessing the acute effects of sotalol on heart function and rhythm following a single dose of the sotalol medication. At the conclusion of your dog’s visit to the VMTH the veterinarian in charge of your dog’s care (attending clinician) may or may not recommend that your dog be sent home on the sotalol medication for longterm therapy. It is possible that a more thorough evaluation of your dog’s heart rhythm with a 24-hour Holter (ECG/”EKG”) monitor is warranted to help determine if long-term therapy is necessary. Please understand that not all ventricular arrhythmias require a long-term antiarrhythmic medication.

Benefits: It is considered standard-of-care to have an echocardiogram (heart ultrasound) performed in dogs with ventricular arrhythmias. If you agree to have your dog participate in this study, the study will cover $159 of the echocardiogram (you will need to pay the remaining $171). The remainder of the cost of your dog’s visit (to be discussed with the attending clinician) will be your responsibility. If adverse events occur directly as a result of the study and your dog requires further care (e.g., hospitalization, monitoring, treatment(s)/medication(s), etc.), the clinical cardiology service will cover up to $3,000 of your dogs care.

We cannot promise any benefits to your dog or other animals from your taking part in this clinical trial; however, possible benefits include allowing us to better guide medical care for your dog and future dogs affected with arrhythmias.

Owner Responsibilities: You will be responsible for bringing your dog in for your scheduled appointment (which will last approximately ½ of the day or 4 hours), covering the $171 of the first echocardiogram, the appointment fee ($140) and whatever else is discussed between you and the attending clinician regarding the management of your dog’s heart disease.

Printable Flyer (PDF)

Pulmonary Hypertension: Understanding the Genetics

Title: The Role of Genetics in Canine Pulmonary Hypertension and the Response to Standard Treatment with Sildenafil

Purpose: We are investigating the role of a common canine genetic variant on the condition of pulmonary hypertension. This genetic variant is being evaluated to see if it impacts the severity of disease or the response to the oral medication, sildenafil citrate, the most commonly used drug for the treatment of this condition. Information provided by this study will provide better guidelines for the treatment of dogs with pulmonary hypertension.

Contact: For more information, please contact Dr. Joshua Stern at or 530-752-2475

Participation Requirements: Dogs diagnosed with pulmonary hypertension

Initial Evaluation for Participation: 

  • Diagnosis of pulmonary hypertension confirmed by a complete echocardiographic study that was done by the UC Davis VMTH Cardiology service; and,
  • A recommendation from the veterinarian to give oral sildenafil for treatment of the condition.

Procedures: If you agree to be involved in this study:

  • Initial visit: We will collect a small blood sample and then perform a non-invasive assessment of blood flow, which will involve shaving a small area (the size of a postage stamp). You will be asked to give the sildenafil orally to your dog as prescribed by your veterinarian.
  • 25-35 days later: We need you to return to the hospital while your pet is receiving the medication to have the echocardiogram, blood sampling and shaved patch for vascular function assessment performed again.
  • You (the owner) will be asked to fill out a brief health questionnaire for your dog at each visit.

Benefits: There is no charge for you to allow your dog to participate in this clinical trial. The study will cover all costs associated with the diagnostic tests, examination fees and the 1-month supply of sildenafil medication. You will be responsible for covering costs associated with any adverse effects that your dog experiences secondary to the prescribed medication.

We cannot promise any benefits to your dog or other animals from your taking part in this clinical trial; however, possible benefits include better understanding of the disease process and mechanisms for predicting patients response to medical therapy.

Owner Responsibilities: You will be asked to complete two brief questionnaires (one at each visit), administer all prescribed medications for at least 30 days, and return while your pet is receiving this medication for a reevaluation appointment at the end of the 30-day period.

Printable Flyer (PDF)