Inspecting the neck for jugular venous distention or abnormal pulsation enables you to crudely estimate systemic venous pressures. Normally, the jugular veins are not distended and collapse quickly after manual compression. Pulsations do not normally traverse greater than one-third the height of the neck in a standing animal. Jugular venous distention or abnormal pulsation may signify right-sided heart failure subsequent to tricuspid insufficiency, dilated cardiomyopathy, pericardial effusion or cardiac tamponade, or constrictive pericarditis. Additional causes may include atrioventricular dissociation, cranial vena caval obstruction, or hypervolemia. Hepatojugular reflux (identifying jugular venous distention while applying steady, firm pressure to the abdomen) is suggestive of right ventricular systolic or diastolic dysfunction, tricuspid valve disease, or pericardial disease.

EVALUATING THE THORAX

Although cardiac auscultation is often the focus when you examine the chest, thoracic palpation and respiratory evaluation are important as well.

Be sure to examine the chest for rib or sternal deformities. Record the pet's inspiratory and expiratory respiratory pattern, including the frequency, regularity, depth, and effort required. Pulmonary auscultation—to detect fluid lines, rhonchi, and wheezes or crackles and rales—usually precedes cardiac auscultation.

Next, identify the location and intensity of the cardiac impulse, and document palpable thrills (vibrations). While the strongest cardiac impulse, or apical beat, is usually identified over the left apex of the heart, the location may be displaced and the strength diminished by any condition that alters the position of the heart, including cardiomegaly, pleural or pericardial effusions, intracavitary masses, or thoracic or pericardial herniations. The location of the apical beat is often a good place to begin cardiac auscultation.

Cardiac auscultation

When performed appropriately, cardiac auscultation can yield tremendous insight into diagnosing cardiovascular disease. Important considerations when performing this technique include using a familiar and comfortable stethoscope, auscultating in a quiet environment, having a thorough understanding of the physiologic and pathologic genesis of cardiac sounds, and, finally, using a combination of practice and patience. Using pediatric stethoscopes for cats and small dogs tends to be based on clinician preference. I use an adult stethoscope for dogs and cats, reserving a pediatric stethoscope for small exotic-animal species.

Since its invention by René Théophile Hyacinthe Laënnec in 1816, the stethoscope has become the almost universal sign of a physician or veterinarian. The modern, binaural stethoscope commonly has a single- or double-tube system composed of ¹ /8-in internal diameter tubing connected to a combination bell and diaphragm. The bell of the stethoscope, lightly applied to the patient to form an airtight seal, accentuates low frequency sounds, and the diaphragm detects high frequency sounds.

Listen for three things during auscultation—heart sounds, heart murmurs, and cardiac arrhythmias.

Heart sounds

Heart sounds are relatively brief, auditory vibrations that can be characterized by their intensity (loudness), frequency (pitch), and quality (timbre).² The basic heart sounds identified in veterinary patients include the first, second, third, and fourth heart sounds (S₁, S₂, S₃, and S₄, respectively). While we identify heart sounds and cardiac murmurs on a daily basis (see the boxed text titled "Standardize your auscultation technique" ), we often fail to recall what physiological and pathophysiological events account for these vital pieces of information.