Carolyn Y Ho MD

Contents

Case Presentation Physiology of Diastole Diastolic Dysfunction

Standard Echocardiographic Assessment of Diastolic Function

Transmitral Doppler Profiles

Abnormal Mitral Inflow Patterns

PV Doppler Flow Patterns

Isovolumic Relaxation Time

Advancements in the Assessment of Diastolic Function Comprehensive Echocardiographic Assessment of Diastolic Function Suggested Reading case presentation

A 63-yr-old female presents to her primary care physician complaining of increased exertional dyspnea. Her exercise tolerance has been slowly declining for the past several months and she occasionally notes orthopnea and paroxysmal nocturnal dyspnea. She has had no anginal symptoms. Her past medical history is notable for hypertension, diabetes, and obesity. Physical examination is notable for poorly controlled blood pressure, elevation of central venous pressures, a fourth heart sound and murmur compatible with mitral regurgitation, and mild lower extremity edema. Echocardiography shows concentric left ventricular hypertrophy and vigorous systolic function without segmental wall motion abnormalities. There is mild mitral regurgitation and moderate left atrial enlargement.

physiology of diastole

Diastole is the portion of the cardiac cycle that spans from isovolumic ventricular relaxation to the completion of antegrade mitral flow. There are four distinct phases of diastole (Fig. 1): (1) isovolumetric ventricular relaxation: an active, adenosine triphos-phate (ATp)-requiring process that occurs from endsystole until left ventricular pressure falls below left arterial pressure leading to mitral valve (Mv) opening; (2) rapid early ventricular filling: blood flows from left atrium (LA) into the left ventricle (LV) during continued, active, then passive LV relaxation; (3) diastasis: active ventricular relaxation is completed and near equilibration of LA and LV pressures occurs with resultant slow LA filling from pulmonary venous (PV) flow; and (4) atrial systole: increased transmitral pressure gradient from atrial contraction results in acceleration of blood flow from LA to LV.

Normal diastolic function is dependent on rapid ventricular relaxation and a compliant chamber. The normal ventricle relaxes quite vigorously leading to rapid pressure decline early in diastole. This contributes to a suction effect that draws blood from the LA into the LV despite relatively low LA pressures. This process is energy-dependent, fueled by the hydrolysis of ATP to release actin and myosin cross-bridges. As such,

From: Contemporary Cardiology: Essential Echocardiography: A Practical Handbook With DVD Edited by: S. D. Solomon © Humana Press, Totowa, NJ

Fig. 1. Cardiac cycle: with spectral doppler relationships. (A) Intracardiac pressures and volumes recorded throughout the cardiac cycle shown with spectral Doppler and volumetric relationships. A, atrial filling; E, rapid early filling; EDV, end-diastolic volume; ESV, end-systolic volume; IVRT, isovolumetric relaxation time.

Cardiac Cycle Mitral Inflow

Fig. 1. Cardiac cycle: with spectral doppler relationships. (A) Intracardiac pressures and volumes recorded throughout the cardiac cycle shown with spectral Doppler and volumetric relationships. A, atrial filling; E, rapid early filling; EDV, end-diastolic volume; ESV, end-systolic volume; IVRT, isovolumetric relaxation time.

diastolic function is vulnerable to disease states that may compromise energy production, such as myocar-dial ischemia. Experimental studies have demonstrated that diastolic function is more sensitive to ischemia than systolic function, with diastolic abnormalities being manifested earlier than systolic function after blood supply is compromised.

Ventricular stiffness or compliance is another critical determinant of proper diastolic function. The normal ventricle is relatively compliant so that small changes in volume are accompanied by proportionally small changes in pressure. Many factors contribute to ventricular stiffness, including intrinsic distensibility and elasticity, wall thickness, cavity dimensions, and pericardial constraint

Table 1

Factors Influencing Left; Ventricular Filling

Left ventricular compliance Intrinsic distensibility and elasticity LV cavity dimensions Rate of relaxation Left atrial compliance Left atrial pressure

Valvular regurgitation: Aortic (AR); Mitral (MR) Pericardial restraint

(Table 1). If compliance decreases, there will be an exaggerated rise in pressure in response to increased volume.

The atria act as reservoir, conduit, and pump during the cardiac cycle, therefore, processes that disrupt normal

Pericardial Restraint
Fig. 2. Normal pressure-volume loop. (A) Ventricular filling. (B) Isovolumetric contraction. (C) Systolic ejection. (D) Isovolumetric relaxation. EDPVR: end-diastolic pressure-volume relationship; ESPVR: end-systolic pressure-volume relationship.
Left Ventricle Presure Volume Loops
Fig. 3. Pressure-volume loop in diastolic dysfunction. The EDPVR in a patient with diastolic dysfunction (shown with dotted line) is shifted upwards and to the left—for any given volume, the diastolic filling pressure acquired to achieve that volume is higher.

atrial function may also contribute to diastolic dysfunction. In young, healthy subjects, atrial contraction contributes approx 20% of ventricular filling. This proportion increases slightly with aging but typically does not exceed 50% of ventricular filling.

diastolic dysfunction

Congestive heart failure is a major public health problem in the United States. Approximately 500,000 new cases are diagnosed annually and it is the most common discharge diagnosis in hospitalized patients. In the majority of cases, heart failure is a result of a combination of systolic and diastolic abnormalities, but in approximately one-third of patients, heart failure symptoms are primarily caused by diastolic dysfunction, as LV systolic function is relatively preserved.

The pathophysiological basis of diastolic dysfunction is that adequate filling of the ventricles, and, therefore, adequate cardiac output, occurs at the expense of abnormal elevation of intracardiac filling pressures. In some instances, intracardiac filling pressures may be normal at rest, but rise precipitously with exercise. This altered pressure-volume relationship (Figs. 2 and 3) can result in symptoms of pulmonary congestion, such as shortness of breath or exercise intolerance. Table 2 lists different causes of diastolic dysfunction as well as conditions that may mimic it.

Table 2

Conditions That Cause or Mimic Diastolic Dysfunction

Conditions associated with diastolic dysfunction

Hypertension

Ischemic heart disease

Hypertrophic cardiomyopathy

Restrictive cardiomyopathy

Constrictive pericarditis and cardiac tamponade

Dilated cardiomyopathy

Cardiac transplant rejection

Conditions that mimic diastolic dysfunction

Pulmonary disease

Deconditioning

Anemia

Thyroid disease Valvular heart disease Congenital heart disease standard echocardiography assessment of diastolic function

Doppler Interrogation of Flow

Traditionally, evaluation of spectral Doppler patterns of mitral inflow has been used to assess LV diastolic function. This approach assumes that transmitral flow velocity is an accurate surrogate for volumetric flow. However, transmitral velocities reflect the pressure

Fig. 4. Normal transmitral flow pattern. Pulse wave Doppler profile of normal transmitral flow during diastole sampled at the tip of the mitral leaflets using the apical four-chamber view. Note the early (E) and atrial (A) velocities representing early and late filling. DT, deceleration time.

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