Background
Systolic reserve is an important compensatory mechanism against increasing afterload. Although longitudinal systolic dysfunction with preserved ejection fraction has been reported in hypertensive hearts, radial and circumferential function has not been fully examined. The aim of this study was to investigate three-directional systolic function and its relationships with left ventricular geometry in asymptomatic hypertensive patients using two-dimensional speckle-tracking imaging.
Methods
Echocardiographic evaluations were performed in 74 hypertensive patients and 55 age-matched control subjects.
Results
Longitudinal strain was significantly reduced in the hypertrophy groups compared with that in control subjects (concentric, −15.1 ± 4.0%; eccentric, −15.9 ± 4.4%; control, −18.9 ± 3.3%; P < .05). Conversely, radial strain was significantly higher in the normal geometry group than in control subjects (53.8 ± 19.4% vs 40.3 ± 15.1%, P < .05). However, this augmentation was attenuated in the other geometries.
Conclusion
Hypertrophic remodeling attenuates compensatory augmentation of radial systolic function and is associated with latent longitudinal systolic dysfunction.
Although diastolic abnormalities are common in elderly asymptomatic patients with hypertension (HTN), other factors that contribute to the progression to diastolic heart failure (DHF) have not been fully elucidated. Recent studies have shown regional myocardial systolic dysfunction using echocardiographic tissue Doppler myocardial velocity not only in patients with DHF but also in asymptomatic patients with HTN. However, the major limitations of this technique are its considerable angle dependency and tethering and translation effect. Furthermore, detailed assessment of myocardial regional function has been difficult because of the complexity of the myocardial architecture.
Two-dimensional speckle-tracking imaging (2DS), a novel echocardiographic technique, is a simple and noninvasive method for assessment of three-directional regional myocardial deformation, which could previously be assessed only by implantation of radiopaque beads in animal hearts or by magnetic resonance myocardial tagging in human hearts. A few studies have shown that longitudinal and radial systolic strain assessed by this technique was decreased in patients with DHF ; however, asymptomatic patients with HTN have not been fully examined. Furthermore, the effect of change in left ventricular (LV) geometry on regional deformation is unknown despite the fact that patterns of abnormal LV geometry have also been associated with adverse outcomes. Patients with increased regional wall thickness without LV hypertrophy have been shown to have poor outcomes similar to those with LV hypertrophy compared with patients with normal LV geometry. However, the mechanism by which altered geometry mediates increased risk is poorly defined.
The aim of this study was to determine three-directional regional systolic function and its relationships with LV geometry in asymptomatic patients with HTN using 2DS.
Methods
Study Population
We retrospectively recruited 626 consecutive subjects who underwent echocardiography for cardiac examination from October 2004 to March 2005 at Sapporo Cardiovascular Hospital and 271 inhabitants of the town of Sobetsu in Hokkaido who underwent annual medical checkups including echocardiography in July 2007. We excluded patients with histories of cardiovascular disease, including atrial fibrillation, moderate or severe valvular heart disease, congestive heart failure and coronary artery disease as indicated by electrocardiography and conventional echocardiography, and renal insufficiency with serum creatinine > 2.0 mg/dL. According to LV geometry as described below, the subjects were divided into four groups of normal geometry, concentric remodeling, concentric hypertrophy (CH), and eccentric hypertrophy (EH). Finally, for additional offline 2DS analysis, we selected 74 uncomplicated hypertensive patients (17 men; mean age, 62 ± 12 years) and 55 age-matched normotensive (NT) subjects with normal geometry (eight men; mean age, 59 ± 10 years) who did not have any cardiovascular diseases as described above or diabetes mellitus. All subjects were in sinus rhythm when the echocardiographic examination was performed. Blood pressure was measured according to the standard procedure in the sitting position just before the echocardiographic examination, and HTN was defined as systolic blood pressure ≥ 140 mm Hg and/or diastolic blood pressure ≥ 90 mm Hg or receiving treatment with antihypertensive drugs. Diabetes mellitus was defined as a fasting blood glucose level ≥ 126 mg/dL, 2-hour postchallenge glucose level ≥ 200 mg/dL, or receiving treatment with hypoglycemic drugs, insulin, or both. Hypercholesterolemia was defined as a total serum cholesterol level ≥ 220 mg/dL. The clinical characteristics of the study population are summarized in Table 1 . Informed consent to participate in this study was obtained from all subjects.
| HT group | |||||
|---|---|---|---|---|---|
| Variable | NT group ( n = 55) | Normal ( n = 24) | CR ( n = 12) | CH ( n = 21) | EH ( n = 17) |
| Age (y) | 59 ± 10 | 62 ± 13 | 60 ± 13 | 64 ± 11 | 61 ± 8 |
| Men | 8 (15%) | 4 (17%) | 2 (17%) | 7 (33%) | 4 (24%) |
| Body mass index (kg/m 2 ) | 22.5 ± 2.6 | 22.6 ± 3.0 | 24.9 ± 3.1 | 26.4 ± 3.3 ∗ † | 25.1 ± 3.4 ∗ |
| Heart rate (beats/min) | 68 ± 10 | 68 ± 13 | 71 ± 13 | 68 ± 7 | 65 ± 13 |
| Systolic BP (mm Hg) | 121 ± 13 | 151 ± 14 ∗ | 155 ± 17 ∗ | 149 ± 15 ∗ | 145 ± 26 ∗ |
| Diastolic BP (mm Hg) | 72 ± 9 | 85 ± 10 ∗ | 88 ± 11 ∗ | 85 ± 9 ∗ | 81 ± 13 ∗ |
| Diabetes mellitus | 0 | 1 (4%) | 1 (8%) | 3 (14%) | 4 (24%) |
| Hypercholesterolemia | 2 (4%) | 2 (8%) | 1 (8%) | 8 (38%) | 6 (35%) |
| Medications | 0 | 3 (12%) | 1 (8%) | 8 (38%) | 7 (41%) |
| Calcium antagonists | 0 | 1 (4%) | 1 (8%) | 8 (38%) | 5 (29%) |
| ACE inhibitors/ARBs | 0 | 2 (8%) | 1 (8%) | 6 (29%) | 3 (18%) |
| β-blockers | 0 | 1 (4%) | 1 (8%) | 4 (19%) | 2 (12%) |
| Echocardiographic parameters | |||||
| LA dimension (mm) | 32 ± 3 | 33 ± 5 | 34 ± 4 | 38 ± 4 ∗ † | 37 ± 4 ∗ † |
| Septal wall thickness (mm) | 8 ± 1 | 8 ± 1 | 10 ± 1 ∗ † | 12 ± 3 ∗ † ‡ § | 10 ± 1 ∗ † |
| Posterior wall thickness (mm) | 8 ± 1 | 8 ± 1 | 10 ± 1 ∗ | 12 ±0 2 ∗ † ‡ § | 10 ± 1 ∗ † |
| RWT (mm) | 0.38 ± 0.04 | 0.39 ± 0.02 | 0.49 ± 0.04 ∗ † § | 0.51 ± 0.09 ∗ † § | 0.40 ± 0.04 |
| LV end-diastolic diameter (mm) | 43 ± 3 | 42 ± 4 | 39 ± 4 ∗ | 47 ± 4 ∗ † ‡ | 49 ± 3 ∗ † ‡ |
| LVMI (g/m 2 ) | 83 ± 20 | 82 ± 18 | 85 ± 19 | 155 ± 48 ∗ † ‡ § | 127 ± 16 ∗ † ‡ |
| LV ejection fraction (%) | 66 ± 4 | 67 ± 6 | 66 ± 5 | 67 ± 4 | 65 ± 6 |
| Doppler parameters | |||||
| E (cm/s) | 65 ± 17 | 64 ± 15 | 67 ± 13 | 55 ± 12 | 68 ± 13 |
| A (cm/s) | 64 ± 16 | 69 ± 11 | 77 ± 16 | 72 ± 14 | 77 ± 14 ∗ |
| E/A ratio | 1.1 ± 0.5 | 1.0 ± 0.3 | 0.9 ± 0.2 | 0.8 ± 0.2 ∗ | 0.9 ± 0.2 |
| Deceleration time of E (ms) | 201 ± 39 | 196 ± 48 | 212 ± 63 | 236 ± 90 | 220 ± 63 |
| Sm (cm/s) | 7.9 ± 1.2 | 7.6 ± 1.3 | 7.7 ± 0.8 | 6.6 ± 1.1 ∗ | 6.9 ± 0.9 |
| Em (cm/s) | 7.9 ± 2.2 | 7.0 ± 1.7 | 7.3 ± 1.5 | 5.0 ± 1.6 ∗ | 5.2 ± 1.0 ∗ |
| Am (cm/s) | 9.2 ± 1.5 | 9.6 ± 1.8 | 9.5 ± 1.9 | 9.0 ± 1.3 | 8.7 ± 1.6 |
| E/Em | 8.4 ± 0.4 | 9.4 ± 0.6 | 9.9 ± 0.8 | 11.8 ± 0.8 ∗ | 13.2 ± 0.9 ∗ † ‡ |
Conventional Echocardiographic Study
A commercially available ultrasound machine (Vivid 7; GE Medical Systems, Milwaukee, WI) equipped with a 2.5-MHz variable-frequency transducer was used for echocardiographic evaluations. Standard echocardiographic views, including parasternal long-axis and apical four-chamber, three-chamber, and two-chamber views, with subjects in the left lateral decubitus position, were obtained in two-dimensional modes. The septal and posterior wall thicknesses at end-diastole, LV end-diastolic and end-systolic diameters, and left atrial (LA) dimension were determined from M-mode echocardiography. LV ejection fraction was calculated using the biplane modified Simpson’s method. Relative wall thickness (RWT) was calculated as the ratio of 2 × posterior wall thickness at end-diastole to LV end-diastolic diameter. LV mass was calculated using the formula proposed by Levy et al. and normalized for body surface area (LV mass index [LVMI]). Increased RWT was defined as ≥0.45 mm, and increased LVMI was defined as ≥131 g/m 2 for men and ≥100 g/m 2 for women. The LV geometric pattern was divided into four groups as previously described, according to RWT and LVMI. Mitral flow parameters, including peak velocities during early diastole (E) and late diastole (A) and E-wave deceleration time, were measured by pulsed-wave Doppler echocardiography, and the E/A ratio was calculated. Each parameter was obtained from an average of three to five measurements. Tissue velocity curves were obtained from online color Doppler tissue imaging analyses in 42 of the controls (76%) and 43 of the patients (58%) with HTN. A sample volume was placed at the septal annulus in the apical four-chamber view, and peak myocardial systolic (Sm), early diastolic (Em), and late diastolic (Am) velocities were measured, and the ratio of mitral to myocardial early diastolic peak velocity (E/Em) was calculated.
LV Systolic Strain Measurements by 2DS
Myocardial strain measurements were performed using 2DS. The analysis was performed offline using commercial software (EchoPAC; GE Medical Systems). After manual tracing of the endocardial border of the end-systolic frame and selecting the appropriate region of interest, including the entire transmural wall, the software automatically determined six segments in each view. Each segmental strain curve was obtained by automatic frame-by-frame tracking of the acoustic markers in the myocardial tissue. The tracking quality was scored as valid or poor. Segments with poor tracking despite manual readjustments of the region of interest were excluded from analysis. Peak systolic longitudinal strain (Ls) was measured in 12 segments (the anteroseptal, anterior, lateral, posterior, inferior, and septal walls at the basal and mid left ventricle) from three apical views and averaged as mean Ls. Peak systolic radial strain (Rs) and circumferential strain (Cs) were measured in six segments (anteroseptal, anterior, lateral, posterior, inferior, and septal) from a mid-LV short-axis view and averaged as mean Rs and Cs, respectively ( Figure 1 ).
