Cardiac Examination & History

In today's world of high-tech cardiology diagnostic techniques, such as echocardiography, the physical examination and historical clinical information may seem obsolete. However, this could not be further from the truth. In fact, an accurate cardiac diagnosis (or at least short differential list) is usually made while the clinician is still in the examining room, based on the results of the physical examination of the patient and questioning of the owner.

In addition, high-tech equipment is often not available in all practices, or access to specialists trained in the use of such equipment is limited. Furthermore, an accurate physical examination and clinical history allow a clinician to focus the diagnostic workup so that superfluous diagnostic tests can be avoided. This reduces the amount of potentially distracting test results as well as financial burden on the client.

STEP BY STEP CARDIAC EXAMINATION & HISTORY

1. InterviewingThere are a few key points to a good clinical history, including body language and listening skills. Closed body language (such as crossed arms) and lack of eye contact can immediately put off clients and will negatively affect the history they can provide. Active listening lets clients know you feel what they are saying is important. Asking questions generated from their previous answer is a very good way to demonstrate active listening. It is also very important to introduce yourself to your patient.

2. Pertinent HistoryThere are no unique aspects to history for cardiovascular disease compared with other diseases. As for any disease, you should determine why the client brought the animal to see you, whether the problem has gotten better or worse, what treatment (if any) has been used, and whether any clinical response (better or worse) to that treatment has occurred. Because many of these animals receive multiple medications, it is strongly suggested to list each medication, the dose, and the frequency of administration (Table 1).

This information is important if new medications will be added or doses changed. Additional questions that may be related to the cardiovascular system include the presence and frequency of coughing, difficulty breathing, and abdominal distension. A history of collapse, especially exercise-induced, could be very important but is uncommonly reported.

3. Physical ExaminationThe physical examination should be done systematically so that the process is consistent between patients and important clinical variables are not overlooked.

The initial physical exam can be accomplished while acquiring the history and includes observing the animal with respect to demeanor, respiratory effort, and overall condition. Once the history has been taken, the "hands on" physical exam can begin.

Arterial PulsesA good first step is palpation of the femoral arterial pulse for strength, symmetry, and synchrony to the apical heartbeat. The strength of the arterial pulse is an indication of left ventricular function. Common causes of reduced pulse strength (quality) include reduced cardiac output from systolic dysfunction (ie, dilated cardiomyopathy), reduced left ventricular filling (ie, pericardial effusion), or delayed left ventricular emptying (ie, subaortic stenosis). The figure shows pressure tracings of arterial blood pressure demonstrating normal pulses (A), bounding arterial pulses (B) (patent ductus arteriosus, aortic insufficiency), weak arterial pulses (C) (dilated ventricular chamber, pericardial tamponade), and bigeminal pulses (D) (alternating pulse deficits) seen with cardiac arrhythmias.

Very strong (bounding) arterial pulses are usually associated with reduced diastolic arterial pulse pressure (ie, patent ductus arteriosus, aortic insufficiency, or arteriovenous fistulae). Peripheral arterial disease is not common in small animal species, but asymmetric femoral arterial pulse quality (in which the pulse is stronger on one side than the other) may be associated with thrombotic disease (as in Cavalier King Charles spaniels) or embolic disease (eg, arterial thromboembolism). Pulse deficits (apical beat with absent or greatly reduced arterial pulse) arise from reduced stroke volume and indicate cardiac arrhythmias. The exact type of arrhythmia must be determined from a surface electrocardiogram.

Procedure Pearl**Pulmonic stenosis and subaortic stenosis, common congenital abnormalities in the boxer dog, result in similar heart murmurs. However, accurate evaluation of femoral arterial pulse quality can usually differentiate these 2 conditions. With pulmonic stenosis, the femoral arterial pulses are of normal strength; with subaortic stenosis, the pulses are usually weak.**

Assessment of pulse quality can be affected by such things as patient obesity or the practitioner's inexperience with evaluating pulse quality. It is important to remember that the physical examination focuses on acquiring information that is supportive of a diagnosis and helps guide additional diagnostic tests. If a practitioner is not confident about interpreting pulse quality, then a concerted effort should be made to increase his or her experience through repetitive evaluation in multiple animals or through continuing education wet labs.

4. Thoracic AuscultationThoracic auscultation allows the examiner to determine whether normal heart sounds are present, muffled, or absent; the presence of abnormal heart sounds; and the presence of normal or abnormal lung sounds. Cardiac auscultation should focus on all cardiac regions; specifically anatomic areas along the thoracic wall that correspond to locations of the cardiac valves (Figures A and B). The mitral valve region (M) is over the area where the apical cardiac beat is palpated. From this location, the pulmonic (P) and aortic (A) areas can be determined. The tricuspid region (T) is located where the apical beat is palpated on the right hemithorax. Abnormal blood flow associated with one of these valves is most commonly heard over the associated areas on the thoracic wall.

It should be emphasized again that all areas of the thorax should be ausculted as important information may be missed if this is not done. An excellent example is the situation with some PDAs: If examiners auscult only the M region, they may hear only a systolic murmur and diagnose mitral regurgitation. However, if they had listened to the left heart base (A and P regions) after listening to the M region, they would have noted the continuous murmur and, when combined with the finding of bounding arterial pulses, would have made the correct diagnosis of PDA.

The normal heart sounds (S1 and S2), along with most pathologic murmurs, are high-frequency heart sounds and are heard best with the diaphragm of the stethoscope. The abnormal "gallop" sounds are low-frequency sounds, and their detection is accentuated with the bell of the stethoscope. The most common type of murmur by far is that occurring during systole; continuous murmurs (those occurring during both systole and diastole) are a distant second (Figure C). Isolated diastolic murmurs are relatively rare. Cats often present with soft systolic murmurs along the parasternal region. These murmurs can be very focal and quite dynamic; the intensity (or loudness) of the murmur can vary considerably or even be absent at times (intermittent murmur).

When the timing of the murmur is combined with the anatomic location where the murmur is loudest, the cause of the murmur can be accurately diagnosed (Table 2). The gallop sounds can be heard with abnormal ventricular filling. The third heart sound (S3) is due to the rapid cessation of ventricular filling associated with a dilated ventricular chamber and occurs in early diastole. The fourth heart sound (S4) occurs when atrial contraction pushes blood into an already stiff ventricle (and occurs during late diastole). The presence of an S3 or S4 is always considered abnormal in the dog and cat.

Gallops can be difficult to hear in any species and are probably harder to hear in cats given their rapid heart rate. Cats usually develop S4 gallops where dogs usually develop S3 gallops. Systolic clicks should never be confused with a gallop as they occur during systole (gallops are diastolic sounds) and clicks are sharp, high-frequency, and short sounds as compared to the low-frequency, dull, and more prolonged sounds of gallops.

Phonocardiograms illustrating murmurs and gallop sounds of common cardiac diseases

**Procedure PearlThe most common cardiac disease encountered in small animal general practice is mitral regurgitation due to endocardiosis. This is usually seen in older animals and most commonly in small breeds. Therefore, it is extremely uncommon to encounter congestive heart failure in an older, small-breed dog when a cardiac murmur is not present.**

5. Mucous MembranesExamination of the mucous membranes allows estimation of tissue perfusion due to the membranes' rich capillary network. Certain changes can indicate alterations to the circulatory system.

• Pale mucous membranes often indicate reduced or poor perfusion, which can be caused by many conditions including poor cardiac output (eg, dilated ventricular chamber, hemodynamically significant cardiac arrhythmias) or intense peripheral vasoconstriction (eg, shock, pain). Pale mucous membranes are also associated with clinically significant anemia.

• Dark red or brick red mucous membranes indicate that the capillary beds are dramatically vasodilated; this is more commonly associated with excessive heat or certain types of shock, such as septic shock.

• Mucous membranes can appear bluish, which is also known as cyanosis. Cyanosis can be further defined as peripheral or central. Peripheral cyanosis is probably the most common clinically recognized form of cyanosis; with this type there is local reduced perfusion of tissues combined with continued or increased oxygen uptake from the blood by the tissue. Good clinical examples of this include slight bluish discoloration of the tongue of obese animals, infracted nail beds or footpads in cats with cardiogenic embolism (Figure A), and the bluish appearance of the distal aspect of human fingers in very cold weather.

Central cyanosis occurs when the circulating blood has more than 5 g/dL of hemoglobin desaturated of oxygen. This can be seen in animals with clinically significant pulmonary disease and hypoxemia or with right-to-left cardiovascular shunts, such as a reverse patent ductus arteriosus and tetralogy of Fallot (Figure B). This right ventricular angiogram demonstrates blood flow from the right ventricle into the aorta (Ao) and pulmonary artery (PA) in a cat with tetralogy of Fallot.

With right-to-left cardiovascular shunts, the mucous membranes can change dramatically and rapidly on the basis of underlying hemodynamic status. As a result, the cyanosis may be present at rest but nearly always worsens with exercise; in fact, it may be noted only when the animal is exercising.

Finally, with reverse patent ductus arteriosus, only the caudal mucous membranes will be cyanotic because the brachycephalic trunk and left subclavian, which supply blood to the head and thoracic limbs, arise proximal to the site of right-sided blood entry (Figure C). This right ventricular angiogram demonstrates blood flow from the right ventricle (RV) crossing the patent ductus arteriosus (*) and into the distal aorta (Ao) in a dog with reverse patent ductus arteriosus. Note that the venous blood from the right ventricle enters the descending thoracic aorta after the origins of the brachycephalic trunk and left subclavian arteries.

Procedure PearlA dog with reverse PDA can present with relatively pink oral mucous membranes but cyanotic caudal mucous membranes (especially with exercise). When evaluating the mucous membranes, be sure to evaluate both the cranial (oral) and caudal (preputial, vulvar) aspects of the body.

6. Jugular VeinsThe final step in the physical examination, and the one most often overlooked, is evaluation of the jugular veins. This allows assessment of right ventricular filling. The animal must be standing (or sitting) with the head in a normal elevated position to allow for accurate assessment.

The most common alteration seen is distension of the jugular vein, which indicates increased right ventricular filling pressures. The latter is most commonly seen with right-sided heart failure from pericardial disease, tricuspid regurgitation, dilated ventricular chamber, heartworm disease, or tricuspid valve stenosis. A distended jugular vein (arrowheads) can also indicate obstruction of flow of the cranial vena cava (ie, cranial caval syndrome) from such things as mediastinal or heart-based masses, thrombi, or vascular stenoses. Abnormal jugular pulsations can also be detected, but these findings are more subtle and can be altered by a bounding carotid pulse underlying the jugular vein. However, a jugular pulse that extends past the thoracic inlet in a dog or cat is considered abnormal and could suggest increased right ventricular filling, severe tricuspid regurgitation, or cardiac arrhythmia.

Cranial caval syndrome is also usually associated with subcutaneous edema in the ventral neck and pectoral region. If the jugular veins are not distended but right-sided heart failure is suspected, a provocative test (hepatojugular reflux) can be used to identify elevated right ventricular filling pressures. The jugular veins are examined while pressure is applied to the cranial abdomen, increasing the amount of blood return to the right heart from the liver. A positive response is distension of the jugular vein while pressure is applied.

7. Differentiating Congestive Heart FailureThere are some additional physical exam findings that may help support, or suggest against, congestive heart failure as the cause of respiratory distress. A consistent hallmark of congestive heart failure is elevated sympathetic tone, which often results in a loss of sinus arrhythmia (very common in dogs) and sinus tachycardia. Therefore, an animal presenting with respiratory distress that has prominent sinus arrhythmia or bradycardia is most often not exhibiting congestive heart failure. Some animals, however, will have concurrent respiratory disease, which can confound the diagnosis. In addition, while uncommon, some animals with severe cardiogenic edema will present with bradycardia, presumably due to hypoxemia.

It should also be mentioned that the most common canine patient with cardiac disease is older and often has multiple concurrent problems. One of the most common is tracheal or lower airway collapse, which can often present with very similar clinical signs to congestive heart failure. The combination of collapsing airways with mitral regurgitation and left atrial enlargement can magnify the clinical signs and make differentiating which condition is most responsible very difficult indeed.

Procedure PearlA positive response to furosemide therapy does not always differentiate congestive heart failure from chronic pulmonary disease as the cause of cough. In some dogs furosemide dries up the secretions associated with underlying pulmonary disease, thereby reducing the stimulus for cough. Your suspicion of cardiac disease as the cause of cough should increase in the presence of heart murmur or cardiomegaly with pulmonary venous congestion on thoracic radiography.