Description
- On auscultation, heart murmurs are sounds that signify abnormal turbulent blood flow in the heart or surrounding blood vessels.
Murmurs can arise from any of the following conditions:
1. Increased Blood Volume
2. Increased Blood Flow Velocity
3. Valve Regurgitation
4. Decreased Blood Viscosity
Types of Heart Murmurs
1. Systolic Heart Murmurs
- Most common type of murmur among small animal patients
- Occur during systole
Functional Murmurs
(Occur without a pathological condition involved)
-Innocent Murmurs (e.g. young animals with temporary murmurs)
-Physiologic/Flow Murmurs (e.g. athletic animals especially thoroughbred horses; conditions such as anaemia, fever, peripheral arteriovenous fistula)
- Aortic flow murmurs are the most common in normal young fit thoroughbred horses
- Valve regurgitations in horses can be functional or pathological (Endocardiosis is the most common form of older equine valve pathology)
Pathological Murmurs
-Atrioventricular valve insufficiency
-Semilunar valve stenosis
-Cardiac shunting (e.g. PDA, VSD)
2. Diastolic Heart Murmurs
- Uncommon in small animals
- Occurs during diastole
Functional Murmurs
(Occur without a pathological condition involved)
-Physiologic/Flow Murmurs (e.g. athletic animals especially thoroughbred horses)
- Ventricular (mitral and tricuspid) flow murmurs are less common in young fit thoroughbred horses compared with aortic flow murmurs, but their presence can still be seen in normal horses.
Pathological Murmurs
-Atrioventricular valve stenosis
-Semilunar valve insufficiency
-Cardiac shunting (e.g. PDA)
3. Continuous Heart Murmurs
- Also called machinery murmurs
- Occur continuously throughout systole and diastole
Pathological Murmurs
-Cardiac shunting (e.g. PDA)
Description of Heart Murmurs
1. Timing/Duration (Systolic, Diastolic, Continuous)
2. Location (Point of Maximal Intensity; Left Side: Heart Base (Semilunar Valves), Heart Apex (Mitral Valve); Right Side: Tricuspid Valve)
3. Intensity (Grading of Heart Murmur is on a scale 1-6)
4. Shape (Description from phonocardiogram:e.g. Holosystolic, Crescendo-decrescendo, Systolic decrescendo, Diastolic decrescendo, Continuous aka Machinery)
5. Sound (Quality & Pitch: High Pitch usually indicates ejection murmurs; Low Pitch usually indicates regurgitant flow murmurs)
6. Radiation (Description based on how far the murmur sound spreads from its point of maximal intensity. e.g. Aortic murmurs=radiate up carotid arteries)
Heart Murmur Grading Scale
| Grade | Description |
|---|---|
| I. | Barely audible (Need ideal conditions to hear) |
| II. | Clearly audible at point of maximal intensity |
| III. | Clearly audible (As loud as S1 & S2; +/- Radiation) |
| IV. | Loud (Louder than S1 & S2; - precordial thrill; Radiation over thorax) |
| V. | Loud (Louder than S1 & S2; + precordial thrill) |
| VI. | Very Loud (Audible with stethoscope lifted off chest; + precordial thrill) |