Cardiology

Do all old dogs with a heart murmur need to be on heart medication?

• No, the presence of a heart murmur, does not automatically warrant treatment.
• In old dogs a heart murmur is most often due to age-related changes of the valves within the heart.
• These changes can make the valves leaky and thereby cause the heart murmur.
• A heart murmur does not necessarily mean that significant heart disease is present
  If the heart is of normal size and no symptoms are observed, treatment is most often not warranted.

When do I need to give heartworm preventative to my dog?

• Risk of heartworm infestation is correlated with lifestyle and signalment.
• Heartworm is transmitted by mosquitos.
• If you live in the Northeast part of the USA you only need to give heartworm preventative from June 1 through November 1, since maturation of the heartworm larvae requires average daily temp. > 64º F (18 ºC) for any one-month period. There is therefore no need to give heartworm chemoprophylaxis year-round, unless administration between June 1 and Nov 1 is occasionally missed.

What is a heart murmur?

• A heart murmur is a sound caused by turbulence in blood flow.
• A murmur can occur if the valves in the heart are leaking, either due to age changes, or in young animals due to developmental defects of the valves or due to abnormal shunting of blood.
• Heart murmurs are graded on a scale of 1 to 6 or 1 to 5.
• Soft murmurs (up to 3/5) may be physiologic and benign.
• High grade murmurs are usually due to pathology (not benign).
• Even if a high grade murmur is present in an old dog, treatment is not always indicated.

My dog has been diagnosed with chronic valve disease. What is that?

• Chronic Valve Disease (CVD) or endocardiosis is a disease secondary to thickening of the heart valves.
• CVD often affects the valve between the left atrium and left ventricle (the mitral valve), causing “backflow” or regurgitation of blood across that valve and therefore a heart murmur.

Do pets get pacemakers?

• Yes, pets do have pacemakers implanted routinely.
• A pacemaker is indicated in cases where the conduction system in the heart is diseased and thereby causing an abnormally low heart rate.
• Often these pets show signs such as weakness or fainting (syncope).

What is pericardial effusion, and why does it occur?

• Pericardial effusion is build up of fluid in the sac surrounding the heart.
• If a large amount of pericardial effusion is present this can compress the heart and prevent it from filling and working properly. When this occurs, cardiac tamponade is said to be present.
• Pericardial effusion can be caused by heart tumors.
• Common types of heart tumors are hemangiosarcomas, which often involve the right atrium, and chemodectomas, which usually surround the aorta and are called heart base tumors.
• At times no obvious reason is found for the pericardial effusion, in which case the etiology is classified as idiopathic.
• If a significant amount of pericardial effusion is present, the heart sounds are muffled, and on chest radiographs the heart silhouette will be globoid.

Which drugs are most often used to treat congestive heart failure in dogs and cats?

• Commonly used drugs are diuretics, angiotension converting enzyme inhibitors and pimobendan.
• Diuretics are used to decrease fluid in lungs, chest cavity and/or abdomen when congestive heart failure is present.
• Furosemide is the most frequently used diuretic.
• An angiotensin converting enzyme inhibitor (ACEI) has many effects including decreasing the myocardial workload.
• Pimobendan is another heart medication which increases contractility of the heart and improves cardiac output.

What are typical signs of heart disease and possible congestive heart failure?

• Typical signs of congestive heart failure are increases in the resting respiratory rate  (breaths per minute) and respiratory effort. These signs are due to accumulation of fluid in the lungs (left sided congestive heart failure) or chest cavity (right sided heart failure).
• Usually the heart rate will be elevated.
• Cough will often be present, especially at night, and if a significant amount of fluid is build up in the lungs significant breathing difficulties will be seen.
• The animal is likely to be intolerant to exercise.
• Left sided heart failure causes fluid accumulation in the lungs, whereas right sided failure causes fluid build up in the abdomen and/or chest cavity.

What are NOT typical signs of heart disease/heart failure?

• Chronic dry cough is NOT a typical sign of heart failure, but may be due to a primary respiratory problem. Chronic cough can however be seen in dogs with severe heart enlargement due to compression of the main stem bronchi, but this type of cough is due to manual compression on the airway and NOT congestion in the lungs.
• Panting is in general NOT a typical sign of heart disease. An animal with congestive heart failure has increased resting respiratory rate (breaths per minute) and effort. In acute cases severe respiratory distress may be seen (open mouth breathing, extended neck, front leg turned outwards – all in order to compensate and improve breathing capability). An animal with these severe signs should be taken to a veterinarian for immediate evaluation.

Is it likely that my pet has significant heart disease if no heart murmur is present?

• No, heart disease without a murmur is rare.
• Especially in old dogs, the absence of a heart murmur would make it very unlikely that significant heart disease or heart failure is present.
• Only in very few conditions can significant heart disease be present without a murmur, but in those instances the clinical symptoms usually give the cardiologist a suspicion of the underlying disease.

My pet had a persistent ductus arteriosus (PDA) diagnosed. What are the treatment options?

• A persistent ductus arteriosus is a congenital heart defect permitting communication between the systemic and pulmonary circulation.
• The communication between the systemic and pulmonary circulation is normal in fetal life, but it should close once the animal is born.
• A large PDA can (if untreated) cause left sided congestive heart failure, and be fatal.
  Treatment options for PDA are either surgery or minimally invasive device occlusion.
• PDA surgery involves opening of the chest cavity and placing a suture around the abnormal vessel connection between the aorta and the pulmonary artery. Device-occlusion (or embolization) is a less invasive procedure performed via catheterization through which a small metal devices is placed within the abnormal vascular connection in order to occlude the shunt.
• Treatment of a PDA (either via surgery or catheterization) is in general curative.

What kind of work-up will be done if I bring my pet to see a cardiologist?

• The cardiologist will initially evaluate your pet by doing a physical examination, which will help establish what further diagnostic work-up is warranted in the individual case. Also the history given by you as the owner is essential in order to provide the best and most appropriate work-up of a given presenting complaint.
• A physical exam done by a cardiologist includes an evaluation of the patient with focus on the cardiovascular system (heart and vessels), which in particular means careful auscultation of the heart (and lungs) to assess whether heart sounds are normal, whether an arrhythmia is present, if the heart rate is within the expected normal range and whether any abnormalities can be heard in the lungs. Also the peripheral pulses, color of mucous membranes and signs of congestive heart failure are assessed (ascites, pleural effusion, edema, etc.).
• There are various further diagnostic tools that may be warranted, but not all may be needed in each case:
• ECG (electrocardiogram): this test evaluates electrical activity of the heart with heart rate (heart beats per minute) and heart rhythm assessment. An ECG can give valuable information about arrhythmias (abnormal heart rhythms) if such are heard on auscultation.
• Echocardiogram (ultrasound of the heart): this diagnostic test gives an opportunity to evaluate the heart’s internal dimension, heart function and valve anatomy by using ultrasound beams that are reflected and transformed to a picture on a monitor. Doppler evaluation is a part of the echocardiographic exam, done in order to assess intra-cardiac blood flow, measure flow velocities, possible shunts, etc.
• Chest radiographs (X-rays): this modality gives information on the lungs , size of lung vessels and the heartsize.
• Holter-monitor: this is a 24 h continuous ECG recording that necessitates the dog wearing a small vest including a mini-recorder, which detects and records every heartbeat over a period of 24 h. Once this recording is analyzed, valuable information about arrhythmias and heart rate can be obtained, which may not have been present when the patient was in the hospital. This diagnostic tool is typically used for patients with a history of syncope (fainting), or if significant arrhythmias are detected in the hospital.
• Event-monitor: this is different from the Holter-monitor in the sense that this device only records when asked. Specifically, this device stores the ECG from the episode of collapse, (when the owner activates the monitor at the time of the event). The advantage with this monitor is that if the syncopal events are infrequent the patient can wear this monitor for several days and the rhythm at the time of an event can be specifically assessed.