Thor Edvardsen

Quantitative assessment of intrinsic regional myocardial deformation by Doppler strain rate echocardiography in humans : validation against three-dimensional tagged magnetic resonance imaging.

Background—Tissue Doppler echocardiography–derived strain rate and strain measurements (SDE) are new quantitative indices of intrinsic cardiac deformation. The aim of this study was to validate and compare these new indices of regional cardiac function to measurements of 3-dimensional myocardial strain by tagged MRI. Methods and Results—The study population included 33 healthy volunteers, 17 patients with acute myocardial infarction, and 8 patients with suspected coronary artery disease who were studied during dobutamine stress echocardiography. Peak systolic myocardial velocities were measured by tissue Doppler echocardiography, peak systolic strain rates and strains by SDE, and strains by tagged MRI. In healthy individuals, longitudinal myocardial Doppler velocities decreased progressively from base to apex, whereas myocardial strain rates and strains were uniform in all segments. In patients with acute infarction, abnormal strains clearly identified dysfunctional areas. In infarcted regions, SDE showed 1.5±4.3% longitudinal stretching compared with −15.0±3.9% shortening in remote myocardium (P <0.001), and radial measurements showed −6.9±4.1% thinning and 14.3±5.0% thickening (P <0.001), respectively. During dobutamine infusion, longitudinal strains by SDE increased significantly from −13.5% to −23.8% (P <0.01) and radial strains increased from 13.1±3.1% to 29.3±11.5% (P <0.01). Comparisons between myocardial strains by SDE and tagged MRI in healthy individuals (n=11), in infarct patients (n=17), and during stress echo (n=4) showed excellent correlations (r =0.89 and r =0.96 for longitudinal and radial strains, respectively, P < 0.001). Conclusions—The present study demonstrates the ability of Doppler echocardiography to measure myocardial strains in a clinical setting. Myocardial strains by Doppler may represent a new powerful method for quantifying left ventricular function noninvasively in humans.

Left Ventricular Concentric Remodeling Is Associated With Decreased Global and Regional Systolic Function The Multi-Ethnic Study of Atherosclerosis

Background—The transition from compensatory concentric remodeling to myocardial failure is not completely understood in humans. To investigate determinants of incipient myocardial dysfunction, we examined the association between concentric remodeling and regional LV function in asymptomatic participants of the Multi-Ethnic Study of Atherosclerosis (MESA). Methods and Results—Myocardial tagged MRI was performed. Regional myocardial function expressed as peak systolic midwall circumferential strain (Ecc) was analyzed in 441 consecutive studies by HARP (Harmonic Phase) tool. Peak Ecc was correlated with the extent of concentric remodeling determined by the ratio of left ventricular mass to end-diastolic volume (M/V ratio). In men, a gradual decline in peak global Ecc was seen with increasing M/V ratio (test for trend, P<0.001). Among women, however, Ecc tended to be lower only in the fifth compared with the first quintile of M/V ratio (P=0.1). The association of lower Ecc with increasing M/V ratio was regionally heterogeneous but was particularly prominent in the LAD region in men (test for trend, P<0.001) and in women (test for trend, P=0.02). In the right coronary and left circumflex artery territories, these associations were less marked in both genders. Conclusions—In this cross-sectional study of asymptomatic individuals, concentric left ventricular remodeling was related to decreased regional systolic function. The reduction in regional function, which was more pronounced in the left anterior descending coronary artery territory, may reflect the local transition from compensatory remodeling to myocardial dysfunction.

Left Ventricular Concentric Remodeling Is Associated With Decreased Global and Regional Systolic Function

Background— The transition from compensatory concentric remodeling to myocardial failure is not completely understood in humans. To investigate determinants of incipient myocardial dysfunction, we examined the association between concentric remodeling and regional LV function in asymptomatic participants of the Multi-Ethnic Study of Atherosclerosis (MESA). Methods and Results— Myocardial tagged MRI was performed. Regional myocardial function expressed as peak systolic midwall circumferential strain (Ecc) was analyzed in 441 consecutive studies by HARP (Harmonic Phase) tool. Peak Ecc was correlated with the extent of concentric remodeling determined by the ratio of left ventricular mass to end-diastolic volume (M/V ratio). In men, a gradual decline in peak global Ecc was seen with increasing M/V ratio (test for trend, P<0.001). Among women, however, Ecc tended to be lower only in the fifth compared with the first quintile of M/V ratio (P=0.1). The association of lower Ecc with increasing M/V ratio was regi...

Coronary Artery Atherosclerosis Is Related to Reduced Regional Left Ventricular Function in Individuals Without History of Clinical Cardiovascular Disease The Multiethnic Study of Atherosclerosis

Objective—We investigated whether regional coronary calcium score by computed tomography is related to regional left ventricular systolic function measured by MRI tagging in participants of the Multiethnic Study of Atherosclerosis. Methods and Results—The Multiethnic Study of Atherosclerosis is a prospective observational study of men and women without a history of previous heart disease from 4 ethnic groups. Calcium scores were measured separately for the left anterior descendent (LAD), left circumflex (LCX), and right (RCA) coronary arteries. Left ventricular strain and strain rate were determined by tagged MRI in the corresponding vascular territories of the coronary vessels in 509 participants. Greater coronary calcification in the LAD, LCX, and right RCA coronary arteries were related to worse function in their respective perfusion. Anterior wall strain rate was −1.37±0.41 when LAD calcium was zero versus −1.17±0.24 1/s in the highest quartile of calcium score (P<0.001). Similar relationships were evident in the LCX and RCA regions. Participants with 1- and 2-vessel coronary artery calcium had better myocardial function in the remote area compared with the territory supplied by the diseased artery. Conclusions—High-local calcium score is related to regional dysfunction in the corresponding coronary territory among individuals without a history of previous heart disease. These results indicate a link between atherosclerosis and subclinical regional left ventricular dysfunction.

Lower Myocardial Perfusion Reserve Is Associated With Decreased Regional Left Ventricular Function in Asymptomatic Participants of the Multi-Ethnic Study of Atherosclerosis

Background— Myocardial ischemia is an important determinant of regional left ventricular systolic function. Myocardial blood flow reserve may be impaired by cardiovascular disease before alterations of myocardial perfusion at rest become manifest. Nevertheless, the relation between flow reserve and regional myocardial function has not been studied in individuals without a history of clinical heart disease. Methods and Results— Seventy-four participants (66±9 years, mean±SD) of the Multi-Ethnic Study of Atherosclerosis (MESA) underwent myocardial magnetic resonance tagging and contrast-enhanced perfusion studies. Regional myocardial function was evaluated as peak systolic circumferential strain (Ecc) in the three main coronary territories (left anterior descending [LAD], left circumflex, and right coronary artery [RCA]). Myocardial blood flow at rest and during adenosine-induced hyperemia was quantified by contrast-enhanced magnetic resonance imaging, to study the relation between regional flow and function after multivariable adjustment for age, gender, body mass index, left ventricular mass, and traditional risk factors. Lower regional myocardial blood flow during hyperemia was associated with reduced regional left ventricular function expressed as lower Ecc in the RCA (P<0.01) and left circumflex regions (P<0.05) measured in the subendocardium, mid-wall, and subepicardium. In contrast, no significant association was seen in the LAD territory (P=0.16). In addition, segmental function in LAD and RCA regions was reduced when individuals in the lowest 10th percentile for regional myocardial flow reserve were compared with the other participants. Absolute decreases in mid-wall Ecc LAD and RCA and global Ecc were 3.0%, 3.4%, and 2.8%, respectively (P<0.05 for all regions). Conclusions— Lower myocardial flow reserve is related to reduced regional function in asymptomatic individuals.

The Influence of Left Ventricular Size and Global Function on Regional Myocardial Contraction and Relaxation in an Adult Population Free of Cardiovascular Disease: A Tagged CMR Study of the MESA Cohort

The purpose of this study is to evaluate the relationship between LV structure and function with regional myocardial function in participants of the Multi-Ethnic Study of Atherosclerosis, which is a prospective study including 4 ethnic groups free from clinical cardiovascular disease. Peak systolic strain (Ecc) and regional strain rates (SRS and SRE) were calculated by harmonic phase from tagged CMR of 1100 participants. The relationships of ejection fraction (EF), end-systolic volume (ESV) and end-diastolic volume (EDV) with Ecc and strain rate were studied before and after adjustment for cardiovascular risk factors. Direct linear relationships between EF and regional systolic and diastolic functions (Ecc, SRS and SRE) were present in almost all of the regions (p < 0.05, i.e., greater EF, greater Ecc, SRS and SRE). LVESV demonstrated a negative relationship with Ecc and SRS (i.e., greater ESV, lower systolic function, indexed by Ecc and SRS) in all regions (p < or = 0.05). LVEDV was inversely related to systolic function, indexed by SR(S) (p < 0.05) in all regions. In conclusion, LVEF is directly related to systolic myocardial function, indexed as the absolute magnitude of systolic strain and strain rate. In addition, left ventricular size, indexed as end-diastolic and end-systolic volumes are inversely related to absolute systolic myocardial strain rate (SRS). These results are crucial to the interpretation of strain alterations induced by left ventricular remodeling in early heart failure.

Tissue Doppler in Ischemic Heart Disease

Tissue Doppler Echocardiography was introduced in the 1960s (Yoshida et al., 1961), and enabled the quantitative assessment of myocardial motion and deformation. The wide use of tissue Doppler as a research tool halted, however, until the early 1990s (Hatle & Sutherland, 2000). Tissue Doppler is now available for high frame rates, wide sector angles and in combination with 2-dimiensional data acquisition. Although widely used in cardiovascular research, the clinical use is limited, probably due to the time consumption associated with special imaging protocols and tedious post processing. Nevertheless, tissue Doppler echocardiography has contributed to most of the available knowledge on the pathophysiology involved in myocardial contraction deficiency. The experienced cardiologist can easily identify large myocardial infarcts by visual analysis of echocardiograms, but identification of a small MI may be challenging due to the modest changes in tissue properties. In ischemic tissue, the contractility is reduced and reduced deformation and deformation rate is observed. Due to differences in contractility among ischemic and adjacent healthy myocardium, the ischemic myocardium has a characteristic deformation pattern with stretch in early systole, reduced systolic shortening, and a delayed (postsystolic) shortening when the ventricular pressure decays. This early stretch and post systolic shortening pattern has been described both experimentally (Edvardsen, T. et al., 2002; Skulstad et al., 2002) and clinically (Gjesdal et al., 2008; Jamal et al., 1999; Voigt et al., 2004).