Photo: Flyer for Clinical Trial for Ventricular Arrhythmias in Dogs

Select for larger image

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)


NEW! Irregular Heartbeat (Ventricular Arrhythmias): Reducing the Risk during Chemotherapy

Title: Use of diphenhydramine to reduced fewer infusion-related ventricular arrhythmias in dogs treated with doxorubicin

Purpose: The current recommendation for canine lymphoma treatment includes the use of a chemotherapy drug called doxorubicin. Although effective, one of the reported side effects of doxorubicin is the liberation of a molecule called histamine, which can cause ventricular arrhythmias (an irregular rhythm). The concurrent use of anti-histamine agents like diphenhydramine (commonly known as Benadryl) with doxorubicin therapy could possibly reduce these abnormal beats. Therefore, the aim of this study is to see if use of diphenhydramine can reduce the risk of arrhythmias sometimes associated with the administration of chemotherapy.


  • Dr. Joshua A. Stern, DVM, PhD, DACVIM (Cardiology) at 530-752-4892 or
  • Dr. Jenna H Burton. DVM, MS, DACVIM (Oncology) at 530-752-0629 or

Participation Requirements: Dogs that have been diagnosed with lymphoma

Initial Evaluation for Participation:  Should you decide to enroll your dog in the clinical trial, your pet would receive a free Echocardiogram screening before receiving Doxorubicin. This would occur at one of the chemotherapy visits prior to the first Doxorubicin treatment.


  • As part of this study, your animal will receive the same diagnostic tests and care that any other dog presented to the Oncology Service would receive. If your dog participated, an anti-histamine drug (diphenhydramine) will be given at only one out of the two study visits.
  • If your dog participated, an anti-histamine drug (diphenhydramine) will be given at only one out of the two study visits.
  • To evaluate the efficacy of diphenhydramine, your dog will wear a portable and battery-operated device that measures heart's activity (Holter monitor) for 3 hours after the infusion of chemotherapy while your dog is still at the VMTH.

Benefits: If you agree to have your dog participate in this study, the screening echocardiogram and your dog’s Holter monitor will be analyzed by a board-certified veterinary cardiologist and will be free of charge. Adverse events are not expected from the use of diphenhydramine; the study will cover up to $3,000 of your dog’s care if any adverse events occur that are attributable to the investigational portion of the study (use of diphenhydramine or not as a pre-medication for doxorubicin) and your dog requires further care (e.g., hospitalization).

Results from this trial may help us to better guide medical care for your dog and future dogs affected with the same disease. The understanding of your dog’s electrocardiogram may guide medical decisions.

Owner Responsibilities: We expect that participation in this clinical trial will last for two visits of the traditional CHOP chemotherapy protocol.

Costs associated with the recommended chemotherapy protocol and patient care will be your responsibility as they are not a part of this study. Additionally, costs associated with side effects that are attributable to doxorubicin administration (decreased appetite, vomiting, diarrhea and/or low white blood cells counts) will not be covered by the study.

Printable Flyer (PDF)

Subaortic or Pulmonic Stenosis: Assessing Two Medications

Title: Echocardiographic effects of butorphanol and atenolol in dogs with subaortic or pulmonic stenosis

Purpose: Pulmonic stenosis (PS) and subaortic stenosis (SAS), the two most common congenital heart defects encountered in dogs, are characterized by a narrowing of the outlet of the right or left side of the heart, respectively. We are studying the effects of two commonly utilized medications – butorphanol, a mild sedative commonly used to help facilitate heart ultrasounds and atenolol, a beta-blocker commonly utilized to help treat PS and SAS – on heart function and assessment of disease severity in dogs with PS and SAS.

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 (530) 979-0751 or (email is preferred). To schedule an appointment, please call (530) 752-1393.

Participation Requirements: Dogs diagnosed with either pulmonic stenosis (PS) or subaortic stenosis (SAS) with a pressure gradient >50 mmHg

Initial Evaluation for Participation:  Dogs must be diagnosed with pulmonic stenosis or (sub)aortic stenosis (pressure gradient >50 mmHg) and be free of any other concurrent cardiac disease to be eligible to participate in this study

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

  • Complete physical examination with particular attention paid to the cardiovascular system and complete echocardiogram (heart ultrasound) without the use of sedatives to confirm diagnosis
  • Blood collection to determine if your dog is affected with a genetic mutation that may cause a lack of response to the atenolol drug
  • Administration of a single standard dose of a sedative, butorphanol (intravenously) and single standard dose of atenolol (orally)
  • 2 more echocardiograms (within 5-20 minutes after administering butorphanol and then 2-3 hours after atenolol administration)

Benefits: All costs associated with the study will be paid for by the study. This includes diagnostics that would be recommended anyway. All dogs previously diagnosed with SAS or PS that are specifically referred for this study will receive a discounted clinical exam and echocardiogram whether they qualify for the study or not. If adverse events occur directly as a result of the study and your dog requires further care (e.g., hospitalization, monitoring, treatment/medications etc), the study will cover up to $3,000 of your dog’s care.

Results from this trial will allow us to better understand and guide medical care for your dog and future dogs affected with pulmonic or subaortic stenosis.

Owner Responsibilities: If you allow your dog to participate in this study, you will be responsible for bringing your dog to the scheduled appointment and covering any costs not related to the study. The study appointment and procedures are anticipated to take approximately 4-5 hours and will consist of only a single visit. You are not required to be present for the entire duration of the visit.

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)