Left Ventricular Hypertrophy

• Myocardial hypertrophy is a response to increased LV wall stress in accordance with Laplace’s law.

• Laplace’s law describes the relationship of wall tension (T) to the transmural pressure difference (P), the radius (r) and thickness (h) of the LV (Figure 5-1).

• High pressure stimulates compensatory increases in wall thickness. Increased volume dilates the cavity and causes higher wall tension for constant pressure, stimulating compensatory LV hypertrophy (LVH) (Figure 5-2).

• Both volume and pressure load influence LVH in hypertension.

• LVH and left ventricular mass (LVM) are strong, independent predictors of all-cause death, congestive heart failure, sudden cardiac death, and other cardiovascular events.

Figure 5-1 Laplace’s law describes the relationship of wall tension and pressure to ventricular size and thickness.

Figure 5-2 Gross pathology of LVH.

How to Evaluate LV Mass

• LV mass may be evaluated using linear, two-dimensional (2D), or three-dimensional (3D) measurements. LV mass is measured by subtracting LV cavity volume from LV epicardial volume to obtain LV myocardial volume, and multiplication of volume by myocardial density to obtain LV mass.

• LVM quantitation requires adequate endocardial and epicardial definition, and on-axis imaging.

Linear Measurements

Key Points

• Linear measurements of interventricular septal wall thickness (SWT), posterior wall thickness (PWT), and LV diastolic internal dimension (LVIDd) should be made from the parasternal long-axis window in end-diastole (Figure 5-3).

• Measurements should be taken at the level of the LV minor axis, at the papillary muscle level.

• Linear measurements can be made directly from 2D images or using 2D-targeted M-mode echocardiography. M-mode recordings aligned perpendicular to the LV long axis may facilitate exclusion of trabeculae and false tendons from the LV wall.

• Linear measurements should be made from leading edge to leading edge.

• To avoid inclusion of RV and LV trabeculae, measurements should be taken from the most rapidly moving myocardial interface.

• Oblique imaging planes may overestimate cavity size and wall thickness (Figure 5-4).

• LVM may be estimated by the following necropsy-validated formula (Figure 5-5):

Figure 5-3 LV linear measurements. A, The endocardial interface (arrows) should be measured from the most rapidly moving myocardial interface to avoid inclusion of RV and LV trabeculae. B, Measurements should be taken at the level of the LV minor axis. C, 2D-directed M-mode measurements in the same patient using the most rapidly moving myocardial interface.

Figure 5-4 3D echocardiography illustrates potential pitfalls in LV measurement due to off-axis imaging. The green, red, and blue lines represent the four-chamber (A), two-chamber, and short-axis planes, respectively, from the 3D volume (B). A correctly oriented LV minor axis plane (C) results in a short-axis image (D) with smaller diameter and thinner apparent wall thickness than an off-axis plane (E and F), without grossly visible differences in short axis.

Figure 5-5 Echocardiographic LV mass has a high correlation (r ≥ 0.90) versus necropsy in humans and experimental animals.

(Reproduced with permission from Devereux RB, Alonso DR, Lutas EM, et al. Echocardiographic assessment of left ventricular hypertrophy: Comparison to necropsy findings. Am J Cardiol. 1986;57:450-458.)

• Relative wall thickness (RWT) may be estimated as:

3D Measurement of LVM

Key Points

• 3D measurement requires high-quality 3D LV volume acquisition with clear endocardial and epicardial interfaces.

• This may be unobtainable with atrial fibrillation or poor acoustic windows.

• Echocardiographic contrast may be useful for poor endocardial definition.

• Select anatomically correct 2- and 4-chamber views with the largest long-axis dimensions (Figure 5-6).

• Epicardial and endocardial contours are traced in the 4-chamber and 2-chamber views at end-diastole. Traced contours are used to calculate LV volumes by use of the biplane Simpson formula similar to 2D measurement of LVM.

• 3D measurement has lower interobserver variability than 2D measurement (Figure 5-7).

Figure 5-6 Reorientation of planes using 3D echocardiography. The four-chamber (A, green), two-chamber (B, red), and short-axis (C, blue) planes are identified by corresponding lines in other projections (D). The short-axis plane is defined by positioning the blue line in both apical views (A and B) at the midpapillary muscle level perpendicular to the long axis of the ventricle. The apical views are iteratively selected by repositioning the red and green lines to pass through the midcavity to the apex, ensuring that the resulting views have the largest long-axis dimension. End-diastolic epicardial and endocardial contours are traced in 4-chamber and 2-chamber views to obtain myocardial volume and mass.

(Reproduced with permission from Mor-Avi V, Sugeng L, Weinert L, et al. Fast measurement of left ventricular mass with real-time three-dimensional echocardiography: Comparison with magnetic resonance imaging. Circulation. 2004;110:1814-1818.)

Figure 5-7 3D measurement of LVM has lower interobserver variability than 2D measurement of LVM. Additionally, 3D measurement of LVM has high agreement with measurement by cardiac magnetic resonance imaging (CMRI).

(Reproduced with permission from Mor-Avi V, Sugeng L, Weinert L, et al. Fast measurement of left ventricular mass with real-time three-dimensional echocardiography: Comparison with magnetic resonance imaging. Circulation. 2004;110:1814-1818.)

Definition of LVH and Abnormal LV Geometry

LV Geometry (Figure 5-8)

Figure 5-8 Definition of abnormal LV geometry.

Key Points

• LV geometry is defined by RWT and LV mass (Figure 5-9).

• Normal LVM with normal or increased RWT is classified as normal LV geometry or concentric LV remodeling.

• LVH (increased LV mass) with normal or increased RWT is classified as eccentric or concentric hypertrophy.

• LV geometry has incremental value for prognostication of mortality (Figure 5-10) and to heart failure events, all-cause mortality, and composite cardiac events (Figures 5-11 and 5-12).

Figure 5-9 Hemodynamic and geometric profiles in hypertensive patients with four patterns of LV geometry. Compared with normal geometry, concentric LV remodeling is associated with lower cardiac output, as lower end-diastolic volume limits SV for the same EF. Concentric LVH is associated with higher systolic blood pressure. Eccentric LVH is associated with higher systolic blood pressure and cardiac output, as higher end-diastolic volumes increase SV for the same EF.

(Reproduced with permission from Ganau A, Devereux RB, Roman MJ, et al. Patterns of left ventricular hypertrophy and geometric remodeling in essential hypertension. J Am Coll Cardiol. 1992;19:1550-1558.)

Figure 5-10 Relationship of LV geometry to mortality in patients with uncomplicated hypertension. Concentric hypertrophy (CH) carries the greatest risk, followed by eccentric hypertrophy (EH) and concentric remodeling (CR). NL, normal.

(Adapted with permission from Koren MJ, Devereux RB, Casale PN, Savage DD, Laragh JH. Relation of left ventricular mass and geometry to morbidity and mortality in uncomplicated essential hypertension. Ann Intern Med. 1991;114:345-352.)

Figure 5-11 LVM and LVH raise the risk of incident heart failure events in the Multi-Ethnic Study of Atherosclerosis.

(Reprinted with permission from Bluemke DA, Kronmal RA, Lima JA, et al. The relationship of left ventricular mass and geometry to incident cardiovascular events: The MESA (Multi-Ethnic Study of Atherosclerosis) study. J Am Coll Cardiol. 2008;52:2148-2155.)

Figure 5-12 Relationship of LV geometry to all-cause mortality and composite cardiac events (cardiovascular death, recurrent myocardial infarction, heart failure, stroke, and resuscitated sudden death) post myocardial infarction in the VALIANT study. Concentric hypertrophy has the highest risk, followed by eccentric hypertrophy and then concentric remodeling.

(Reproduced with permission from Verma A, Meris A, Skali H, et al. Prognostic implications of left ventricular mass and geometry following myocardial infarction: The VALIANT (VALsartan In Acute myocardial iNfarcTion) Echocardiographic Study. JACC Cardiovasc Imaging. 2008;1:582-591.)