| A complete physical examination should be performed on any animal being evaluated for heart disease. In addition to auscultation of the thorax, palpation should be performed to assess for the presence of thrills (low frequency vibrations that can be palpated with the fingertips) and alterations in intensity or location of the impulse beat. Concurrent auscultation and palpation of pulses should also be performed. Mucous membrane color and refill time, as well as assessment for
jugular pulsation and excessive distention, is recommended. Limbs should be examined for the presence of edema, and the abdomen should be assessed for the presence of ascites. |
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Heart Sounds and Murmurs: |
| Heart sounds are generated by the rapid acceleration and deceleration of blood and secondary vibrations in the cardiohemic system. Four heart sounds can potentially by ausculted. The first heart sound (S1) is associated with closure of the atrioventricular (AV) valves, and the second heart sound (S2) is associated with closure of the semilunar (aortic and pulmonic) valves. The third heart sound (S3) occurs in
early diastole and is a result of rapid ventricular filling, and the fourth heart sound (S4) is associated with atrial systole. In horses, all 4 sounds can be audible. In cattle, typically only S1 and S2 are audible, although S3 or S4 can sometimes be heard. IV fluid administration in cattle can result in accentuation of the third and/or fourth heart sounds. In dogs,
cats, and ferrets, S1 and S2 are normally the only heart sounds audible. Less is known about goats, sheep, and pigs; however, only the first and second heart sounds are believed to be audible in these species. |
Gallop Heart Sounds:
| A gallop heart sound is the presence of the first and second heart sounds accompanied by an interceding sound that is either an accentuated third or fourth heart sound, or both. These are classified as
protodiastolic (S3),
presystolic (S4), or
summation gallop heart sounds (fusion of S3 and S4). The most common gallop heart sound noted in dogs is a result of an accentuated third heart sound and typically occurs secondary to myocardial disease such as dilated cardiomyopathy or degenerative valve disease. An S4 gallop heart sound (presystolic) can be audible in cats with cardiomyopathy. Because the heart rate commonly exceeds 160-180
bpm in cats, gallop heart sounds are typically summation gallop heart sounds. A
systolic click is a short, sharp, often transient sound that can occur during mid- to late systole. These clicks are uncommon in dogs and probably in other domestic species and are most commonly noted in dogs with early myxomatous degeneration of the mitral valve. They usually are single but may be multiple or may disappear completely in some cycles. |
Splitting of S1 or S2 :
| This may occur in the absence of other cardiac abnormalities. The first heart sound is due to passive closure of the mitral and tricuspid valves. S1 may be markedly split when the contraction of the 2 ventricles is asynchronous, as in bundle-branch block, cardiac pacing, and certain ectopic ventricular beats, resulting in differential closure of the AV valves. Splitting of S1 can also occur in normal healthy, large-breed dogs.
S2 may be split during inspiration in dogs (especially large-breed dogs) and typically results from an increase in negative intrathoracic pressure during inspiration, increased right ventricular filling, and consequent delayed closure of the pulmonic valve relative to the aortic valve. Splitting of S2 is a normal finding in horses during either inspiration or expiration. The second heart sound is produced by passive closure of
the aortic and pulmonic valves. Abnormal splitting of S2 is associated with pulmonary hypertension, as in pulmonary emphysema of horses and heartworm infestation of dogs. Other causes in dogs (and possibly other species) include atrial septal defect, pulmonic stenosis, right or left bundle-branch block, and certain ventricular ectopic beats. Delayed closure of the aortic valve (such as with subaortic stenosis, left bundle branch block, certain ectopic
ventricular beats, or systemic hypertension) can result in paradoxical splitting of S2 (the pulmonic valve closes prior to the aortic valve). |
Synchronous Diaphragmatic Flutter:
| The diaphragm may contract synchronously with the heart to produce loud thumping noises on auscultation and usually visible contraction in the flank area. The syndrome results from stimulation of the phrenic nerve by atrial depolarization and occurs primarily when there is a marked electrolyte or acid-base imbalance, particularly with hypocalcemia. It is most common in horses and dogs and occurs frequently in eclampsia. It is seen most commonly in dogs in association with
electrolyte disturbances induced by GI disease. |
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Murmurs: |
| Heart murmurs are audible vibrations emanating from the heart or major blood vessels and generally are the result of turbulent blood flow or vibrations of cardiac structures such as part of a valve leaflet or chordal structure. Murmurs are typically defined relative to timing, intensity, and location, but can also be characterized by frequency (pitch), quality (eg, musical), and configuration (eg, crescendo-decrescendo). A
systolic murmur occurs during systole and is typically either ejection (crescendo-decrescendo) or regurgitant (holosystolic, plateau). Ejection systolic murmurs demonstrate the greatest intensity during mid-systole and appear diamond-shaped on phonocardiography. They can be produced by stenotic lesions at the semilunar valves (eg, pulmonic stenosis or subaortic stenosis). Regurgitant systolic murmurs demonstrate a constant intensity throughout systole and can be caused by mitral or tricuspid regurgitation (eg, myxomatous degeneration of the mitral valve).
Diastolic murmurs are typically decrescendo (decreasing in intensity through diastole) and a result of aortic or pulmonic insufficiency (such as that caused by aortic valve infective endocarditis).
Continuous murmurs are most commonly a result of patent ductus arteriosus (a congenital cardiac defect) and occur throughout systole and diastole. Continuous murmurs vary in intensity over time, typically being most intense at the end of ventricular ejection and decreasing in intensity through diastole. A
to-and-fro murmur occurs in patients that demonstrate both a systolic murmur and a diastolic murmur and can occur in patients with a ventricular septal defect and aortic valve insufficiency or in a patient with subaortic stenosis and aortic insufficiency. |
| In horses, early systolic and diastolic murmurs can be noted in the absence of heart disease or anemia. The point of maximum intensity is typically located over the left heart base. A short, high-pitched, squeaking, early diastolic cardiac murmur is sometimes seen in healthy young horses. Occasionally, systolic murmurs are noted in some cats secondary to an increase in right midventricular flow velocity without significant structural heart disease. Innocent cardiac murmurs are
also commonly noted in immature cats and dogs (<6 mo of age) as a result of increased stroke volume. |
| Heart murmurs are classified as follows: Grade I—the lowest intensity murmur that can be heard, typically detected only while auscultation is performed in a quiet room; Grade II—a faint murmur, easily audible, and restricted to a localized area; Grade III—a murmur immediately audible when auscultation begins; Grade IV—a loud murmur immediately heard at the beginning of auscultation but not accompanied by a thrill; Grade V—a very loud murmur with a
palpable thrill, the loudest murmur that is still inaudible when the stethoscope is just removed from the chest wall; or Grade VI—an extremely loud murmur that can be heard when the stethoscope is just removed from the chest wall. |
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Arrhythmias: |
| Arrhythmias are abnormalities of the rate, regularity, or site of cardiac impulse formation and are noted during auscultation. Other terms such as dysrhythmia and ectopic rhythm are also used to describe arrhythmias. The presence of a cardiac arrhythmia does not necessarily indicate the presence of heart disease; many cardiac arrhythmias are clinically insignificant and require no specific
therapy. Some arrhythmias, however, may cause severe clinical signs such as syncope or lead to sudden death. Numerous systemic disorders may be associated with abnormal cardiac rhythms. (For discussion of specific arrhythmias, see
Electrocardiography.) |
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Pulses: |
| A pulse is the rhythmic expansion of an artery that can be digitally palpated (or visualized) during physical examination. Physiologically, the pulse pressure is the difference between systemic systolic and diastolic pressures. In dogs and cats, pulses are typically palpated at the femoral artery. Jugular venous pulsation can be noted in normal animals. These pulses typically do not extend beyond a third of the distance up the neck of an animal in a standing position.
Pulse deficits are absent pulses despite auscultation of a heart beat and are thus detected during simultaneous auscultation and pulse palpation. These occur as a result of ectopic ventricular contractions (arrhythmias) that occur so prematurely (rapidly) that the ventricles are unable to fill sufficiently to result in ejection of blood.
Bounding pulses (an increase in pulse pressure) can be noted in patients with aortic insufficiency or patent ductus arteriosus.
Weak pulses (a reduction in pulse pressure) can be noted in patients with heart failure or subaortic stenosis. Dogs with severe subaortic stenosis may demonstrate a pulse pressure that slowly increases during ventricular systole and reaches a peak pressure late in systole called
pulsus parvus et tardus .
Pulsus paradoxus is a decrease in pulse pressure during inspiration and an increase in pulse pressure during expiration. This is a normal occurrence in animals, but, it is usually too subtle to observe on physical examination. Patients with pericardial effusion and cardiac tamponade, however, demonstrate an exaggeration of this finding.
Pulsus alternans is an alternating strong and weak pulse while the patient is in sinus rhythm; it can be noted (albeit rarely) in patients with myocardial failure or tachyarrhythmias.
Pulsus bigeminus is an alternating strong and weak pulse caused by an arrhythmia such as ventricular bigeminy. The weaker pulse (during the ventricular premature contraction) typically follows a shorter time interval than the stronger pulse. |
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Respiratory Sounds: |
| Pulmonary edema may develop as a result of CHF. On physical examination, this may manifest as respiratory crackles and wheezes. Dyspnea or tachypnea may also be noted in these patients. A decrease in air movement is commonly present during thoracic auscultation in patients that have developed pleural effusion as a result of heart disease. However, respiratory diseases or pleural effusion secondary to other underlying disease can also result in these clinical signs. |
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Ascites: |
| Abdominal swelling may occur as a result of gas, soft tissue, or fluid accumulation. Patients with heart disease and right-sided heart failure (such as caused by heartworm disease or tricuspid valve dysplasia) can develop ascites. |
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