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VETERINARY CLINICAL CARDIOLOGY
CARDIOLOGY CONCEPTS
Clinical Evaluation of Heart Disease
The Physical Exam
1. What are the historical findings in heart failure?
  • Syncope/lethargy - due to reduced cerebral perfusion.
  • Weakness/reduced stamina - due to reduced skeletal muscle perfusion.
  • Dyspnea/wheeze/cough/orthopnea - Dyspnea is due to pulmonary edema or pleural effusion. Cough may occur due to pulmonary edema or due to mitral valve insufficiency with left atrial enlargement and compression of the left main-stem bronchus; this latter cause may often occur in the absence of congestive heart failure. Many dogs with heart failure may not cough, whereas dyspnea, wheezes and sometimes orthopnea (difficulty breathing when lying down) are common historical findings. Some dogs will cough with relatively mild edema and others only cough with severe pulmonary edema. It appears that the speed with which the pulmonary edema develops may play a role in determining when or if cough is to develop.
  • Abdominal distention - due to ascites and/or
  • Hepatomegaly or splenomegaly.
2. What are the physical examination findings in heart failure?
Physical examination findings may include (signs of both reduced cardiac output and elevated preload):

  • slow capillary refill time (> 2 sec)
  • pale or cyanosed mucous membranes
  • dry or tacky mucous membranes
  • cool extremities or reduced rectal temperature
  • jugular venous distention or positive hepato-jugular reflux test
  • dyspnea, cough, harsh lung sounds, wheezes, or crackles on auscultation
  • thrill on precordial palpation
  • cardiomegaly on precordial palpation
  • hepatomegaly and/or splenomegaly
  • abdominal effusion
  • subcutaneous edema
  • weak femoral arterial pulse
  • pulse deficits with irregular cardiac rhythm
  • muffled heart sounds, gallop rhythms, heart murmurs, or arrhythmias may be detected on cardiac auscultation

Explanation of Auscultatory findings to follow.

3. What are pulse deficits?
Pulse deficits are present when the pulse rate is less than the heart rate. This occurs because a cardiac contraction or several contractions take place prematurely not allowing enough time for ventricular filling (preload). This results in heart beats that do not eject enough blood to generate a palpable pulse.

The presence of pulse deficits should alert the diagnostician to the occurrence of premature ectopic beats. These may be either supraventricular or ventricular in origin, only the ECG can distinguish these.

4. What is a hepato-jugular reflux (HJR) response?
This test checks for the presence of jugular distention or jugular pulsations when pressure is placed in the region of the cranial abdomen in a ventral to dorsal direction. The animal should be standing or in sternal recumbency to perform this test.

A positive test result indicates that there is elevated pressure in the right atrium or right ventricle. If one were to classify an elevated pressure in the right heart as mild, moderate or severe, venous distention at rest indicates a severe elevation in pressure, whereas a positive HJR indicates a moderate elevation in pressure. Patients with a mild elevation in pressure to the right heart cannot be identified on physical examination.

5. How do I interpret the arterial pulse?
The arterial pulse may be classified as weak, normal, or strong.

The palpable strength of the pulse is determined by:

  • the Pulse Width (known as Pulse Pressure) = Systolic Pressure - Diastolic Pressure
  • the rate of change from systolic to diastolic pressure and back again to systolic pressure

The arterial pulse (through the effect of systolic and diastolic pressure) is affected by:

  • left ventricular stroke volume
  • ejection velocity
  • the relative compliance and capacity of the arterial system
  • the pressure waves that result from the antegrade flow of blood and reflections of the arterial pressure pulse returning from the peripheral circulation
The most exuberant arterial pulses occur with patent ductus arteriosus and aortic valve insufficiency. Strong arterial pulses occur with enhanced sympathetic tone (anemia, hyperthyroidism, and fever). Weak arterial pulses occur with reduced stroke volume or aortic stenosis.

Comment: The arterial pulse can be maintained near normal in the face of a reduced cardiac output, mainly due to the effect of the compensatory arterial vasoconstrictor mechanisms.

6. What diagnostic aids are available to evaluate the heart?
7. What abnormalities can be detected by cardiac palpation?
Precordial palpation is useful to: 

  • detect a thrill - a thrill refers to a vibration on the chest wall due to fluid turbulence within the heart that also causes a heart murmur on auscultation. Only the very loudest heart murmurs will be accompanied by a thrill
  • detect dysrhythmias
  • suspicion of cardiomegaly
  • location of apex beat - usually on left - some disorders will cause the apex beat to shift to the right chest wall
8. What can be learned from auscultation?
Auscultation remains the most useful and expedient assessment of the cardiac patient. It can frequently result in a definitive diagnosis or when combined with the signalment and history can often provide a strong differential diagnosis.

The goals of auscultation are:

  1. To determine the heart rate

  • Bradycardia, normal, or tachycardia
    1. To determine if there is a rhythm disorder

  • To be distinguished from a respiratory arrhythmia
    1. To rule out muffled or absent heart sounds

  • Occur due to insulation between sound source and stethoscope as in:
    • Presence of fluid in the pericardial space = pericardial effusion
    • Presence of fluid in the pleural space = pleural effusion
    • Mass in the pleural space or pericardial space
      • Pleural tumors
      • Pericardial tumors
      • Diaphragmatic hernia either to the pleural or pericardial space
    • Lung parenchymal disease
    • Obesity
  • May be a normal variant in some dogs
    1. To rule out extra sounds such as

  • Heart murmurs
  • Gallop sounds: S3 or S4 or summation
  • Systolic clicks
  • Split heart sounds: S1 or S2
  • Pericardial friction rubs - rare in small animals
  • Other than for detecting asystole, auscultation cannot provide definitive evidence of heart failure. Rarely, individuals may have heart failure in the face of normal heart sounds and cardiac rhythm. The finding of gallop sounds is often very strong evidence of severe myocardial dysfunction. The presence of a murmur does not equate with heart failure. In fact, most patients with a heart murmur do not have heart failure.

    To hear examples of normal and abnormal heart sounds, see Heart Sounds of the Month

    9. What are some important technical aspects about stethoscopes and auscultation?
    1. Most of the disorders that promote abnormal heart sounds produce sounds that do not fall into the audible range. Thus, to detect those few that do fall into the audible range, careful auscultation is necessary to locate these sounds.

    2. For the best sound reproduction, consider the following:

  • A double lumen scope is better than a single lumen
  • Shorter tubing is better than longer tubing
  • The best results occur if the room is quiet and one person is dedicated to controlling the head of the patient including closing the mouth to reduce panting. An attempt should be made to promote ease of breathing and reduce anxiety on the part of the patient.
  • The diaphragm is better for high frequency sounds such as most systolic murmurs, clicks, and breath sounds
  • The bell is better for low frequency sounds such as diastolic murmurs, and gallop sounds. If the bell is pressed tightly to the skin, the skin will function like a diaphragm and so the utility of using a bell will be lost.
  • 3. Only auscult a patient when in the standing or sitting position. Auscultation of the patient in lateral or dorsal recumbency can result in creating false murmur like sounds (perhaps rubbing sounds) and/or impairs our ability to localize the PMI for a "real" murmur.

    10. What is the origin of the normal heart sounds, S1 and S2?

    S1

  • High frequency sound
  • Heard best over the left apex
  • With respect to timing: is associated with closure of the AV valves
  • It signals the onset of systole and correlates in timing with the QRS of the accompanying ECG.
  • Origin is controversial. Probably due to the rapid deceleration of the column of blood into the ventricle at the end of filling which sets the heart into vibration.
  • The intensity of S1 is probably mainly related to the velocity of closure of the AV valves.
  • S2

  • High frequency sound
  • Heard best over the left base
  • With respect to timing: is associated with closure of the semilunar valves
  • It signals the end of ventricular ejection and occurs corresponding to after the end of the T wave on an accompanying ECG.
  • Origin is controversial.
  • The intensity of S2 probably increases as the velocity of semilunar valve closure increases.
  • 11. What are heart murmurs?
    Heart murmurs are abnormal, extra sounds that are of a relatively long duration.
    Heart murmurs occur as a result of turbulence within the heart created by disturbed blood flow.

    Reynolds number defines the variables that promote disturbed (non laminar) flow in a vessel or chamber. When Reynolds Number exceeds a critical value flow becomes turbulent.

    Reynolds No = (Area)(Velocity)(Density) / Viscosity

    Area = cross-sectional area of the chamber, orifice, or vessel; Velocity = velocity of blood flow (note that this is related to the area); Density = density of blood; Viscosity = viscosity of blood (affected mainly by the red blood cell count and protein count)

    Blood flow turbulence can be created by high-velocity flow, flow from a narrow region into a larger area, or low blood viscosity.

    12. What causes heart murmurs?
    1. Causes of turbulence:
    • Valvular insufficiency
    • Valvular stenosis
    • Connections between the cardiac chambers (i.e. interatrial and interventricular defects (holes)
    • Connections between the great vessels (i.e. PDA)
    1. Not associated with organic disease:
      • May be innocent / physiologic associated with low blood viscosity (anemia, hypoproteinemia)
        • < grade 3
        • occur in early to mid systole
        • Note that if blood viscosity is increased, a murmur may be masked
      • May be observed in young adults likely associated with ejection of blood into the great vessels
        • < grade 3
        • occur in early to mid systole
      • Associated with increase in blood flow across a normal valvular orifice as with flow across the pulmonic valve in a VSD and ASD or across the aortic valve in bradycardia such as 3rd degree AV block

    Anything that muffles the heart sounds can obscure a murmur such as obesity, thoracic effusions, or loud respiratory sounds.

    13. Can heart murmurs occur in the absence of anatomic or physiologic changes to the heart?
    Functional (physiologic) heart murmurs occur in the absence of cardiac disease in a variety of situations. These murmurs are most commonly identified in the growing young dog, where they are referred to as innocent murmurs. These murmurs should resolve by 6 months of age, and tend to have the following characteristics:
    • soft, low intensity sounds (grade 1/6 to 2/6)
    • occur early in systole
    • PMI over the left base
    • may vary in intensity with a change in HR or body position

    It is my belief that similar innocent heart murmurs may also occur in the adult, particularly of large and giant breed dogs.

    Functional (physiologic) murmurs may also occur:

    • in athletes
    • in pathologic states such as fever, anemia, or hypoproteinemia

    These are important features to distinguish innocent murmurs from congenital heart murmurs.

    14. How does the detection of a heart murmur help us determine the type of heart disease?
    A presumptive diagnosis is usually possible based primarily on the timing of the heart murmur, and the point of maximal intensity (PMI) of the murmur.

    Note that other features of the murmur also aid in identifying the etiology and they include:
  • The intensity (loudness)
  • The frequency (pitch)
  • The configuration (shape)
  • The quality
  • The duration
  • The direction of radiation
  • These "other features" are clearly of secondary use and less sensitive than the primary features of timing and PMI.

    1. Point of Maximal Intensity (PMI):

    The PMI refers to the location where the murmur is loudest.

    The left chest wall is typically divided with respect to PMI into two positions.

    • left heart base (includes both the pulmonic valve and aortic valve areas, and discriminating between these two is often problematic)
    • left heart apex (mitral valve area)

    The right chest wall is typically divided with respect to PMI into two positions.

  • mid heart (tricuspid valve area)
  • sternal border (typical of a VSD)
    1. Timing:

    Timing of murmurs, at the PMI, is generally divided into one of three classes:

  • systolic (occurring during systole)
  • diastolic (occurring during diastole)
  • continuous (present at all times)
  • Systolic murmurs:

    • The very vast majority of murmurs are systolic
    • When soft they are usually early in systole and disturb the end of S1. S1 often appears slurred in these cases as opposed to ending abruptly as is normally the case.
    • The careful clinician focuses on the end of S1 for soft systolic murmurs.
    • Holosystolic murmur: refers to a systolic murmur that begins during or immediately after S1 and ends with the onset of S2
    • Pansystolic murmur: refers to a systolic murmur that begins during or immediately after S1 and continues into and obscures S2 (note that left ventricular pressure continues to be greater than left atrial pressure after aortic valve closure - during isovolumetric relaxation).

    Systolic Murmur Examples:


    Diastolic murmurs:

    • Very rare
    • Low frequency
    • Rather low intensity and so are graded out of 4, not 6
    • Best identified with the bell of the stethoscope

    Continuous murmurs:

    • Common, but less so than systolic
    • Typically associated with a PDA, but also arteriovenous fistulas
    • Usually vary in intensity throughout the cardiac cycle, however the murmur is detected at all times
    • The continuous nature of the murmur may only be noted at the PMI, while at other locations it may only be systolic, for example.

    Continuous Murmur Examples:

    To and Fro murmurs:

    • The name for the situation when a systolic murmur and a diastolic murmur (due to different physiologic etiologies) coexist.

    To and fro Murmur Example:

    Using the timing and PMI of a murmur, the following algorithm may be used to arrive at a presumptive diagnosis:

    Recall causes for a continuous murmur: PDA or Arteriovenous Fistula

    1. Intensity:

    The intensity of the murmur at its origin is related to (Blood flow velocity) x (Rate of flow). Overall, the intensity of a heart murmur is not related to the severity of the lesion; however for some diseases there is a rough correlation between the intensity of the murmur and the severity of the lesion such as:

    • Mitral valve insufficiency
    • Aortic / subaortic valve stenosis
    • Pulmonic valve stenosis

    The intensity of a murmur is graded on a scale of 1 to 6:

  • Grade 1 = a very soft, localized murmur detected only after several minutes of listening.
  • Grade 2 = a soft murmur, heard immediately but localized to a small area.
  • Grade 3 = a moderately intense murmur that is readily detected and detected over more than one location.
  • Grade 4 = a moderately intense or loud murmur, detected over several areas, usually both sides of the chest, however a precordial thrill is not detected in this case.
  • Grade 5 = a loud murmur accompanied by a precordial thrill over the point of maximal intensity.
  • Grade 6 = a very loud murmur accompanied by a precordial thrill and the murmur is detected when the stethoscope is pulled slightly off the chest wall.
  • 15. What are some special considerations for heart murmurs in cats?
  • In the cat, the areas of typical location for murmurs in dogs are not useful. Murmurs are typically loudest located along the sternum or just off the right or left side of the sternum. Murmurs can be located in the caudal part of the thorax or cranial part of the thorax in the cat.
  • Cranial sternal murmurs in cats are common, usually functional, and probably due to ejection of blood into a dilated aorta or dynamic right ventricular outflow tract obstruction.
  • VSD is probably the most common congenital cause for a murmur.
  • MR is probably the most common acquired cause for a murmur.
  • About 20-25% of murmurs in cats are not associated with any substantial pathology.
  • S3 and S4 sounds are louder than in dogs, greater intensity and higher frequency.
  • S4 gallops may be normal in older stressed cats. Since their heart rates are usually high it can be difficult to discriminate between an S3 and an S4 in the cat.
  • 16. What other abnormalities may be detected by cardiac auscultation and what is their significance?

    1. GALLOPS:

    • result in a tripling or quadrupling of the heart sounds, resembling the canter of a horse
    • best heard with the bell of the stethoscope

    S3 gallop (ventricular gallop)
    • Low frequency sound
    • Occurs shortly after the S2 sound, at the beginning of diastole, during the rapid filling phase.
    • Called a ventricular gallop
    • Not normal in dogs and cats. Indicates ventricular failure. May be an early finding and the only auscultatory evidence of heart failure.
    • Indicates diastolic dysfunction
    • Associated with reduced compliance of the ventricle while filling under conditions of high filling pressures (stiffer ventricle).
    • Caused by the sudden termination of longitudinal expansion of the ventricular wall during brisk early diastolic filling during the period of rapid ventricular filling.
    • Indicates severe myocardial disease

    S4 gallop (atrial gallop)

    • Low frequency sound
    • Occurs shortly before the S1 sound, at the end of diastole, during atrial contraction.
    • Called an atrial gallop
    • Not normal in dogs and cats. Usually indicates ventricular failure. May be the only auscultatory evidence of heart failure.
    • Indicates diastolic dysfunction
    • Associated with the atria trying to force blood into an already over-distended ventricle or because the atria are forcing blood into a stiff ventricle. Atrial contraction is required for an audible S4 sound. Thus it does not occur in atrial fibrillation.
    • Occurs in disorders with impaired relaxation of the ventricle typical of disorders of concentric hypertrophy
    • May be a normal finding in older stressed cats

    Summation gallop

    • At fast heart rates an S3 and S4 gallop will superimpose to cause one sound called a summation gallop.

    Example 1

    1. CLICKS:

    • Abnormal sounds
    • Very high frequency sounds
    • Most commonly associated with mitral valve disease
    • Uncommon finding overall in small animals, but mainly found in dogs, not cats
    • When present in mid to late systole, are associated with mitral valve disease, likely prolapse
    • When present in early systole, are associated with aortic or pulmonic stenosis
    Example 1

    1. SPLIT HEART SOUNDS:

    • A split S1 is due to asynchronous closure of the AV valves, which may occur with conduction disturbances such as bundle branch block or ectopic ventricular beats or with mechanical disturbances in valve closure such as mitral or tricuspid stenosis.
    • A split S2 is due to asynchronous closure of the semilunar valves. This may be heard in normal large breed dogs during inspiration as there is more right ventricular filling and longer right ventricular ejection time during inspiration. Abnormal causes of split S2 include 1) conduction disturbances such as bundle branch block and ectopic ventricular beats, 2) delayed closure of the pulmonic valve such as with pulmonary hypertension, pulmonic stenosis, or an atrial septal defect, or 3) delayed closure of the aortic valve such as with systemic hypertension or aortic stenosis.
    Split S1

    1. FRICTION RUBS:

    • More common in large animals
    • Scratchy sounds
    • May have a:
      • periodicity with the heart rhythm (then it is difficult to distinguish from a continuous murmur)
      • periodicity with respiration
    • caused by fibrin present on the pleural surfaces of chest wall, lungs, or pericardium

    1. ARRYTHMIAS:

    • Isolated premature beats or pairs or short bursts of premature beats result in disturbances to the cadence of the heart rhythm.
    • Premature beats may result in only the presence of abnormally long pauses between beats. If the premature beat is extremely early (premature) no additional heart sounds will be detected, only the presence of the abnormal pause that follows. One might suspect that so-called "dropped beats" are occurring. PVCs tend to cause longer pauses than SVPCs.
    • If the premature beat is slightly less premature only an S2 will be detected, so that the rhythm will sound like S1 then S2 and another S2 in rapid succession. This could be misinterpreted as a gallop. Gallops should not be intermittent like premature beats and they are not followed by an abnormal pause.
    • Even less premature beats may be associated with both an early S1 and S2.
    • A regular rhythm does not mean the rhythm is necessarily normal/sinus. Sustained ventricular or supraventricular tachycardia can be associated with a regular rhythm.
    Example 1

    1. ABNORMAL RESPIRATORY SOUNDS:

    • Wheezes
      • High pitched expiratory sounds typical of bronchial narrowing
    • Crackles (formerly called rales or rhonchi)
      • High pitched inspiratory sounds typically detected at the end of inspiration
      • Subtle crackles may only be detected with a deep inspiration
      • Sound like Velcro pulled apart or radio static
      • Caused by explosive opening of small airways
      • May be due to pulmonary edema, small airway disease (bronchitis), pulmonary fibrosis, or pneumonia
      • The loudest crackles are associated with airway disease
    Example 1
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