Presentation on theme: "CARDIAC VALVE DEFECTS John Wood, PhD Depts of Molecular & Integrative Physiology and Surgery Office: 1014 Smith East Phone: 588-7478"— Presentation transcript:
CARDIAC VALVE DEFECTS John Wood, PhD Depts of Molecular & Integrative Physiology and Surgery Office: 1014 Smith East Phone:
OBJECTIVES After the completion of the lectures and reading assignments the student should be able to: For aortic insufficiency, aortic stenosis, mitral insufficiency, mitral stenosis, pulmonic insufficiency, pulmonic stenosis, tricuspid insufficiency, and tricuspid stenosis: 1. describe the expected auscultation sounds that define each valve. 2. state whether a murmur occurs in systole or diastole. 3.describe the change in pressure with time during systole and diastole on each side of the defective valve, and how this change relates to the intensity of the murmur. 4.describe the acute and chronic changes resulting from pressure or volume changes within chambers of the heart.
The diagram above shows the optimal locations for hearing specific murmurs. Mitral and tricuspid valve murmurs are best heard in the apical region with the tricuspid valve adjacent to the sternum and the mitral valve more lateral. Aortic and pulmonic valve murmurs are heard best at the level of the 2nd or 3rd intercostal space, with the aortic valve on the right side of the sternum and the pulmonic valve on the left side of the sternum. LOCATING CARDIAC VALVE MURMURS
TYPES OF MURMURS
The sound or intensity of a murmur is characterized as: 1.decrescendo: loud at the beginning and decreases in intensity 2.crescendo-decrescendo: low volume at the onset, increases in intensity, and then decreases in intensity (also called a "diamond shaped" murmur). 3.decrescendo-crescendo: loud at the beginning and decreases in intensity, then increases in intensity again near end of murmur 4.holo (also called pan): relatively constant loudness CLASSIFICATION OF MURMURS
Murmurs are categorized as a: 1.systolic murmur: begins with or after the first heart sound and ends at or before the second heart sound (S1 to S2). 2.diastolic murmur: begins with or after the second heart sound and ends before the first heart sound (S2 to S1). SYSTOLIC MURMUR DIASTOLIC MURMUR AORTIC REGURGITATIONAORTIC STENOSIS MITRAL STENOSISMITRAL REGURGITATION
INTENSITY OF A MURMUR The intensity of the murmur is directly related to the magnitude of the flow across the defective valve, which is dependent on the pressure gradient across the valve driving flow. In the example of aortic stenosis above, the intensity of the murmur is dependent on ΔP across the valve, which is P LV – P aorta. FLOW
AORTIC STENOSIS The aortic valve leaflets do not open completely (stiff valve), which reduces the size of the opening through which blood is ejected (increased resistance to flow). The stenotic aortic valve increases the resistance to left ventricular ejection (greater afterload), even though total peripheral resistance is not changed.
The murmur is dependent on the pressure difference across the aortic valve: Left ventricular pressure - Aortic pressure The murmur begins upon aortic valve opening and continues throughout ventricular systole (until aortic valve closure, S2). The pressure difference across the stenotic aortic valve is initially low as ejection begins, and rises as ventricular pressure increases above aortic pressure until it reaches a peak at the midpoint of ventricular systole. As ventricular pressure falls during the slow ejection phase, the pressure difference across the valve then decreases until aortic closure occurs. This results in a systolic crescendo- decrescendo murmur. AORTIC STENOSIS: INTENSITY OF THE MURMUR ∆P across valve
Because of the high resistance to ejection in the stenotic aortic valve, the rate of ejection of blood is decreased. As a result, aortic pressure rises more slowly than normal and the pulse pressure is reduced. The time for left ventricular systole will be prolonged (while the time for left ventricular diastole is shortened). This causes paradoxical splitting of S2. A hallmark of aortic stenosis is a large pressure difference between the left ventricle and aorta during ventricular systole. AORTIC STENOSIS: ARTERIAL PRESSURES
AORTIC STENOSIS: CHRONIC CHANGES The increased afterload due to high resistance of the stenotic aortic valve will lead to left ventricular hypertrophy over time (left axis deviation). The Po line will shift upward and to the left due to the hypertrophy, and the diastolic filling curve will shift upwards due to decreased compliance of the ventricle. Left atrial pressures will be increased due to decreased ventricular compliance, which may result in atrial hypertrophy. Aortic stenosis may severely restrict increases in cardiac output (i.e., exercise).
AORTIC INSUFFICIENCY Aortic insufficiency (regurgitation) occurs when the aortic valve leaflets fail to close completely. The murmur begins upon incomplete closure of the aortic valve (S2). Backflow of blood occurs from the aorta to the left ventricle during ventricular diastole.
CONSEQUENCES OF BACKFLOW FROM AORTA TO LEFT VENTRICLE The backflow of blood across the incompetent aortic valve will result in an abnormal route of: 1. filling of the left ventricle (with acute and chronic effects) 2. runoff of blood from the arterial system.
AORTIC INSUFFICIENCY: INTENSITY OF THE MURMUR Dependent on the pressure difference across the aortic valve: Aortic pressure - Left ventricular pressure This pressure difference decreases throughout diastole as aortic pressure decreases and left ventricular pressure increases (due to filling). This results in a diastolic decrescendo murmur. ∆P across valve
AORTIC INSUFFICIENCY: ARTERIAL PRESSURE A key feature of aortic insufficiency is low diastolic pressure. Because of the backflow of blood from the aorta to the left ventricle, blood volume in the arterial system decreases faster than normal during diastole, even though total peripheral resistance (TPR) is unchanged (and so the rate of venous runoff is unchanged).
Pulse pressure is increased in aortic insufficiency. Left ventricular end diastolic volume (LVEDV) is increased since ventricular filling now results from two routes: from the left atrium as well as backflow from the aorta. The increase in LVEDV above normal is equal to the amount of the regurgitation. The greater LVEDV will increase stroke volume (SV) compared to normal, and this will produce a larger pulse pressure and higher arterial systolic pressure. AORTIC INSUFFICIENCY: ARTERIAL PRESSURE
AORTIC INSUFFICIENCY: STROKE VOLUME The amount of blood ejected from the left ventricle during systole will be greater than that in the right ventricle (stroke volumes during systole are different between ventricles). However, not all of the blood ejected from the left ventricle reaches systemic organs as some blood flows backwards into the left ventricle. The "effective" left ventricular stroke volume (which is the volume which flows to the systemic organs) is less than its systolic stroke volume.
AORTIC INSUFFICIENCY: CHRONIC CHANGES Chronic overfilling of the ventricle results in left ventricular hypertrophy (left axis deviation). The hypertrophied ventricle can generate greater force due to increased muscle mass (left shift in the Po curve compared to normal). Hypertrophy results in decreased compliance of the left ventricular wall so the left ventricular diastolic filling curve will be shifted upwards. As a result, left ventricular EDP will be increased and causing pressures upstream to increase (increased left atrial pressure, pulmonary venous pressure, pulmonary capillary pressure, and cause pulmonary edema). A chronic rise in left atrial pressure can lead to atrial hypertrophy (seen as an enlarged P wave).
MITRAL INSUFFICIENCY Mitral insufficiency is failure of the mitral valve leaflets to close completely. During ventricular systole, blood is pumped in two directions: into the aorta and backwards into the left atrium. Systolic murmur
MITRAL INSUFFICIENCY: INTENSITY OF THE MURMUR Dependent on the pressure difference across the mitral valve: Left ventricular pressure - Left atrial pressure Because of the high ventricular pressure, the pressure difference remains relatively large throughout systole (although left atrial pressure rises markedly). The murmur remains loud and constant throughout systole (holosystolic murmur). Left atrial pressure will be markedly increased due to backflow across the incompetent mitral valve. ∆P across valve
The elevated atrial pressure can result in hypertrophy of the left atrium (seen as an enlarged P wave). Left ventricular hypertrophy can result from a chronic elevation in left ventricular volume. MITRAL INSUFFICIENCY: CHRONIC CHANGES
MITRAL STENOSIS The mitral valve leaflets do not open completely (stiff valve). The murmur occurs in ventricular diastole. The stenotic mitral valve increases the resistance to blood flow into the left ventricle.
MITRAL STENOSIS: INTENSITY OF THE MURMUR Dependent on the pressure difference across the mitral valve: Left atrial pressure - Left ventricular pressure This pressure gradient is highest at the beginning of rapid ventricular filling. As blood enters the ventricle, left atrial pressure falls during diastole. The progressive fall in the pressure gradient across the mitral valve produces a diastolic decrescendo murmur. When atrial contraction occurs, left atrial pressure rises and the pressure gradient is increased, resulting in a presystolic crescendo murmur. ∆P across valve
MITRAL STENOSIS: CHRONIC CHANGES In mitral stenosis, left atrial pressure is markedly elevated throughout the entire cardiac cycle. The high left atrial pressure results in higher pressures upstream: increased pulmonary venous pressure, and increased pulmonary capillary pressure (which promotes filtration in the lung, and pulmonary edema). Pulmonary edema impairs O 2 transport and reduces O 2 levels in lung tissue. Hypoxia causes pulmonary arterioles to constrict, which raises pulmonary vascular resistance and increases pulmonary arterial pressure. A chronic increase in pulmonary artery pressure will result in right ventricular hypertrophy and right axis shift.
MITRAL STENOSIS: CHRONIC CHANGES People with this valve dysfunction have a limited ability to increase cardiac output (which may limit physical activity). The elevated atrial pressure can result in hypertrophy of the left atrium (seen as a notched P wave). Mitral stenosis cannot result in left ventricular hypertrophy since ventricular filling is impaired.
The characteristics of right heart valve dysfunction are the same as for the corresponding valve in the left heart. For example, both pulmonic and aortic stenosis will produce a crescendo- decrescendo murmur. The location of the valve dysfunction (right vs left heart) can be determined by examining: A. where pressure changes occur (i.e., right atrial pressure will be increased with tricuspid stenosis) B. axis shifts (i.e., pulmonic stenosis will cause right axis deviation) C. whether the murmur gets louder during inspiration (right side valve defect) or expiration (left side valve defect) VALVE DYSFUNCTIONS IN THE RIGHT HEART
MNEMONIC TO PREDICT SYSTOLIC OR DIASTOLIC MURMURS VALVE DEFECT MURMUR AORTIC REGURGITATION DIASTOLIC AORTIC STENOSIS SYSTOLIC MITRAL STENOSIS DIASTOLIC MITRAL REGURGITATION SYSTOLIC (H)ARD ASS MSD MRS The first two letters in the mnemonic define the valve defect (skip the “H” in “HARD”. The last letter in the mnemonic defines when the murmur is heard, either in systole or diastole.
CARDIAC VALVE DEFECT MNEMONIC VALVE DEFECT MURMUR. AORTIC REGURG. DIASTOLIC DECRESCENDO AORTIC STENOSIS SYSTOLIC CRESCENDO/- DECRESCENDO MITRAL STENOSIS DIASTOLIC DECRESCENDO- PRESYSTOLIC CRESCENDO MITRAL REGURG. SYSTOLIC HOLO or PAN (H)ARD ASS MSD MRS FALL BUMP YOU THROUGH
SUMMARY OF CARDIAC VALVE DEFECTS
In mitral stenosis and tricuspid stenosis, there is: Impaired filling of the corresponding ventricle (no hypertrophy of this ventricle). A diastolic decrescendo-presystolic crescendo murmur.