Kristina H. Haugaa

Mechanical Dispersion Assessed by Myocardial Strain in Patients After Myocardial Infarction for Risk Prediction of Ventricular Arrhythmia

OBJECTIVES The aim of this study was to investigate whether myocardial strain echocardiography can predict ventricular arrhythmias in patients after myocardial infarction (MI). BACKGROUND Left ventricular (LV) ejection fraction (EF) is insufficient for selecting patients for implantable cardioverter-defibrillator (ICD) therapy after MI. Electrical dispersion in infarcted myocardium facilitates malignant arrhythmia. Myocardial strain by echocardiography can quantify detailed regional and global myocardial function and timing. We hypothesized that electrical abnormalities in patients after MI will lead to LV mechanical dispersion, which can be measured as regional heterogeneity of contraction by myocardial strain. METHODS We prospectively included 85 post-MI patients, 44 meeting primary and 41 meeting secondary ICD prevention criteria. After 2.3 years (range 0.6 to 5.5 years) of follow-up, 47 patients had no and 38 patients had 1 or more recorded arrhythmias requiring appropriate ICD therapy. Longitudinal strain was measured by speckle tracking echocardiography. The SD of time to maximum myocardial shortening in a 16-segment LV model was calculated as a parameter of mechanical dispersion. Global strain was calculated as average strain in a 16-segment LV model. RESULTS The EF did not differ between ICD patients with and without arrhythmias occurring during follow-up (34 +/- 11% vs. 35 +/- 9%, p = 0.70). Mechanical dispersion was greater in ICD patients with recorded ventricular arrhythmias compared with those without (85 +/- 29 ms vs. 56 +/- 13 ms, p < 0.001). By Cox regression, mechanical dispersion was a strong and independent predictor of arrhythmias requiring ICD therapy (hazard ratio: 1.25 per 10-ms increase, 95% confidence interval: 1.1 to 1.4, p < 0.001). In patients with an EF >35%, global strain showed better LV function in those without recorded arrhythmias (-14.0% +/- 4.0% vs. -12.0 +/- 3.0%, p = 0.05), whereas the EF did not differ (44 +/- 8% vs. 41 +/- 5%, p = 0.23). CONCLUSIONS Mechanical dispersion was more pronounced in post-MI patients with recurrent arrhythmias. Global strain was a marker of arrhythmias in post-MI patients with relatively preserved ventricular function. These novel parameters assessed by myocardial strain may add important information about susceptibility for ventricular arrhythmias after MI.

Myocardial strain imaging: how useful is it in clinical decision making?

Abstract Myocardial strain is a principle for quantification of left ventricular (LV) function which is now feasible with speckle-tracking echocardiography. The best evaluated strain parameter is global longitudinal strain (GLS) which is more sensitive than left ventricular ejection fraction (LVEF) as a measure of systolic function, and may be used to identify sub-clinical LV dysfunction in cardiomyopathies. Furthermore, GLS is recommended as routine measurement in patients undergoing chemotherapy to detect reduction in LV function prior to fall in LVEF. Intersegmental variability in timing of peak myocardial strain has been proposed as predictor of risk of ventricular arrhythmias. Strain imaging may be applied to guide placement of the LV pacing lead in patients receiving cardiac resynchronization therapy. Strain may also be used to diagnose myocardial ischaemia, but the technology is not sufficiently standardized to be recommended as a general tool for this purpose. Peak systolic left atrial strain is a promising supplementary index of LV filling pressure. The strain imaging methodology is still undergoing development, and further clinical trials are needed to determine if clinical decisions based on strain imaging result in better outcome. With this important limitation in mind, strain may be applied clinically as a supplementary diagnostic method.

Left ventricular mechanical dispersion by tissue Doppler imaging: a novel approach for identifying high-risk individuals with long QT syndrome

Aims The aim of this study was to investigate whether prolonged and dispersed myocardial contraction duration assessed by tissue Doppler imaging (TDI) may serve as risk markers for cardiac events (documented arrhythmia, syncope, and cardiac arrest) in patients with long QT syndrome (LQTS). Methods and results Seventy-three patients with genetically confirmed LQTS (nine double- and 33 single-mutation carriers with previous cardiac events and 31 single-mutation carriers without events) were studied. Myocardial contraction duration was prolonged in each group of LQTS patients compared with 20 healthy controls (P < 0.001). Contraction duration was longer in single-mutation carriers with previous cardiac events compared with those without (0.46 ± 0.06 vs. 0.40 ± 0.06 s, P = 0.001). Prolonged contraction duration could better identify cardiac events compared with corrected QT (QTc) interval in single-mutation carriers [area under curve by receiver-operating characteristic analysis 0.77 [95% confidence interval (95% CI) 0.65–0.89] vs. 0.66 (95% CI 0.52–0.79)]. Dispersion of contraction was more pronounced in single-mutation carriers with cardiac events compared with those without (0.048 ± 0.018 vs. 0.031 ± 0.019 s, P = 0.001). Conclusion Dispersion of myocardial contraction assessed by TDI was increased in LQTS patients. Prolonged contraction duration was superior to QTc for risk assessment. These new methods can easily be implemented in clinical routine and may improve clinical management of LQTS patients.

Right ventricular mechanical dispersion is related to malignant arrhythmias: a study of patients with arrhythmogenic right ventricular cardiomyopathy and subclinical right ventricular dysfunction.

AIMS We evaluated if right ventricular (RV) mechanical dispersion by strain was related to ventricular arrhythmias (VT/VF) in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) and if mechanical dispersion was increased in so far asymptomatic mutation carriers. METHODS AND RESULTS We included 69 patients, 42 had symptomatic ARVC and 27 were mutation positive asymptomatic family members. Forty healthy individuals served as controls. Myocardial strain was assessed in 6 RV and 16 left ventricular (LV) segments. Contraction duration (CD) in 6 RV and 16 LV segments were measured as the time from onset R on electrocardiogram to maximum myocardial shortening in each segment. The standard deviation of CD was defined as mechanical dispersion. Mechanical dispersion was more pronounced in ARVC patients with arrhythmias compared with asymptomatic mutation carriers and healthy individuals in RV [52(41,63) vs. 35(23,47) vs. 13(9,19)ms, P < 0.001]. Mechanical dispersion was more pronounced in asymptomatic mutation carriers compared with healthy individuals (P < 0.001). Right ventricular mechanical dispersion predicted VT/VF in a multivariate logistic regression analysis [odds ratio (OR), 1.66 (95% confidence interval (CI) 1.06-2.58), P < 0.03]. Right ventricular and LV function by strain were reduced in symptomatic ARVC patients and correlated significantly (R = 0.81, P < 0.001). Right ventricular and LV strain were reduced in asymptomatic mutation carriers compared with healthy individuals (P < 0.001). CONCLUSION Right ventricular mechanical dispersion was pronounced in patients with ARVC with VT/VF. Right ventricular mechanical dispersion was present in asymptomatic mutation carriers and may be helpful in risk stratification. Right ventricular and LV function correlated in ARVC patients implying that ARVC is a biventricular disease.

Strain Echocardiography Improves Risk Prediction of Ventricular Arrhythmias After Myocardial Infarction

OBJECTIVES The aim of this study was to test the hypothesis that strain echocardiography might improve arrhythmic risk stratification in patients after myocardial infarction (MI). BACKGROUND Prediction of ventricular arrhythmias after MI is challenging. Left ventricular ejection fraction (LVEF) <35% is the main parameter for selecting patients for implantable cardioverter-defibrillator therapy. METHODS In this prospective, multicenter study, 569 patients >40 days after acute MI were included, 268 of whom had ST-segment elevation MIs and 301 non-ST-segment elevation MIs. By echocardiography, global strain was assessed as average peak longitudinal systolic strain from 16 left ventricular segments. Time from the electrocardiographic R-wave to peak negative strain was assessed in each segment. Mechanical dispersion was defined as the standard deviation from these 16 time intervals, reflecting contraction heterogeneity. RESULTS Ventricular arrhythmias, defined as sustained ventricular tachycardia or sudden death during a median 30 months (interquartile range: 18 months) of follow-up, occurred in 15 patients (3%). LVEFs were reduced (48 ± 17% vs. 55 ± 11%, p < 0.01), global strain was markedly reduced (-14.8 ± 4.7% vs. -18.2 ± 3.7%, p = 0.001), and mechanical dispersion was increased (63 ± 25 ms vs. 42 ± 17 ms, p < 0.001) in patients with arrhythmias compared with those without. Mechanical dispersion was an independent predictor of arrhythmic events (per 10-ms increase, hazard ratio: 1.7; 95% confidence interval: 1.2 to 2.5; p < 0.01). Mechanical dispersion and global strain were markers of arrhythmias in patients with non-ST-segment elevation MIs (p < 0.05 for both) and in those with LVEFs >35% (p < 0.05 for both), whereas LVEF was not (p = 0.33). A combination of mechanical dispersion and global strain showed the best positive predictive value for arrhythmic events (21%; 95% confidence interval: 6% to 46%). CONCLUSIONS Mechanical dispersion by strain echocardiography predicted arrhythmic events independently of LVEF in this prospective, multicenter study of patients after MI. A combination of mechanical dispersion and global strain may improve the selection of patients after MI for implantable cardioverter-defibrillator therapy, particularly in patients with LVEFs >35% who did not fulfill current implantable cardioverter-defibrillator indications.

Vigorous physical activity impairs myocardial function in patients with arrhythmogenic right ventricular cardiomyopathy and in mutation positive family members

Exercise increases risk of ventricular arrhythmia in subjects with arrhythmogenic right ventricular cardiomyopathy (ARVC). We aimed to investigate the impact of exercise on myocardial function in ARVC subjects.

Transmural Differences in Myocardial Contraction in Long-QT Syndrome Mechanical Consequences of Ion Channel Dysfunction

Background— Long-QT syndrome (LQTS) is characterized by prolonged myocardial action potential duration. The longest action potential duration is reported in the endomyocardium and midmyocardium. Prolonged action potential duration in LQTS may cause prolonged cardiac contraction, which can be assessed by strain echocardiography. We hypothesized that myocardial contraction is most prolonged in subendocardial myofibers in LQTS patients and that inhomogeneous transmural contraction is related to the risk of spontaneous arrhythmia. Methods and Results— We included 101 genotyped LQTS mutation carriers and 35 healthy individuals. A history of cardiac arrhythmias was present in 48 mutations carriers, and 53 were asymptomatic. Myocardial contraction duration was assessed by strain echocardiography as time from the ECG Q wave to peak strain in 16 LV segments. Strain was assessed along the longitudinal axis, predominantly representing subendocardial fibers, and along the circumferential axis, representing midmyocardial fibers. Mean contraction duration was longer in LQTS mutation carriers compared with healthy individuals (445±45 versus 390±40 milliseconds; P<0.001) and longer in symptomatic compared with asymptomatic LQTS mutation carriers (460±40 versus 425±45 milliseconds; P<0.001). Contraction duration by longitudinal strain was longer than by circumferential strain in symptomatic LQTS patients (460±45 versus 445±45 milliseconds; P=0.008) but not in asymptomatic patients and healthy individuals, indicating transmural mechanical dispersion. This time difference was present in a majority of LV segments and was most evident in patients with LQT2 and the Jervell and Lange-Nielsen syndrome. Conclusion— Contraction duration in symptomatic LQTS mutation carriers was longer in the subendocardium than in the midmyocardium, indicating transmural mechanical dispersion, which was not present in asymptomatic and healthy individuals.Background— Long-QT syndrome (LQTS) is characterized by prolonged myocardial action potential duration. The longest action potential duration is reported in the endomyocardium and midmyocardium. Prolonged action potential duration in LQTS may cause prolonged cardiac contraction, which can be assessed by strain echocardiography. We hypothesized that myocardial contraction is most prolonged in subendocardial myofibers in LQTS patients and that inhomogeneous transmural contraction is related to the risk of spontaneous arrhythmia. Methods and Results— We included 101 genotyped LQTS mutation carriers and 35 healthy individuals. A history of cardiac arrhythmias was present in 48 mutations carriers, and 53 were asymptomatic. Myocardial contraction duration was assessed by strain echocardiography as time from the ECG Q wave to peak strain in 16 LV segments. Strain was assessed along the longitudinal axis, predominantly representing subendocardial fibers, and along the circumferential axis, representing midmyocardial fibers. Mean contraction duration was longer in LQTS mutation carriers compared with healthy individuals (445±45 versus 390±40 milliseconds; P <0.001) and longer in symptomatic compared with asymptomatic LQTS mutation carriers (460±40 versus 425±45 milliseconds; P <0.001). Contraction duration by longitudinal strain was longer than by circumferential strain in symptomatic LQTS patients (460±45 versus 445±45 milliseconds; P =0.008) but not in asymptomatic patients and healthy individuals, indicating transmural mechanical dispersion. This time difference was present in a majority of LV segments and was most evident in patients with LQT2 and the Jervell and Lange-Nielsen syndrome. Conclusion— Contraction duration in symptomatic LQTS mutation carriers was longer in the subendocardium than in the midmyocardium, indicating transmural mechanical dispersion, which was not present in asymptomatic and healthy individuals. # Clinical Perspective {#article-title-34}

Left Ventricular Function Assessed by Two-Dimensional Speckle Tracking Echocardiography in Long-Term Survivors of Hodgkin's Lymphoma Treated by Mediastinal Radiotherapy With or Without Anthracycline Therapy

Anthracycline therapy is well known for its adverse cardiac effects. However, few studies have been performed of the long-term follow-up of myocardial function in adult survivors of Hodgkins lymphoma receiving anthracycline. Two-dimensional speckle tracking echocardiography is an accurate angle-independent modality for the quantification of left ventricular (LV) function. The aim of the present study was to investigate the long-term effect of anthracycline on LV systolic function. Echocardiography was performed in 47 survivors of Hodgkins lymphoma 22 ± 2 years after successful mediastinal radiotherapy with (n = 27) or without (n = 20) anthracycline (doxorubicin) treatment and in 20 healthy controls. LV function was assessed by the LV ejection fraction and global longitudinal and circumferential strain. Both patient groups had received a similar dosage of radiation, and doxorubicin was given at a total dose of 309 ± 92 mg. The global longitudinal strain was reduced in patients receiving anthracycline with mediastinal radiotherapy compared to the other group receiving mediastinal radiotherapy alone or combined radiotherapy and regimens without anthracyclines (-16.1 ± 1.9% vs -17.5 ± 1.7%, respectively, p <0.05). Both patient groups had reduced strain compared to the healthy controls (-20.4 ± 1.7%, both p <0.001). The circumferential strain was also reduced in the treatment groups (-18.3 ± 3.2% and -17.8 ± 3.6% vs -22.5 ± 2.1%, both p <0.001). The LV ejection fraction did not differ between the patient groups (55 ± 8% vs 56 ± 6%, p = 1.0) but was reduced compared to that of the controls (62 ± 5%, both p <0.05). In conclusion, myocardial function was reduced in the survivors of Hodgkins lymphoma 2 decades after successful treatment consisting of mediastinal radiotherapy with or without chemotherapy. Patients receiving anthracycline therapy had additional negative long-tem effects on LV systolic function.

The use of echocardiography in acute cardiovascular care: recommendations of the European Association of Cardiovascular Imaging and the Acute Cardiovascular Care Association.

Echocardiography is one of the most powerful diagnostic and monitoring tools available to the modern emergency/critical care practitioner. Currently, there is a lack of specific European Association of Cardiovascular Imaging/Acute Cardiovascular Care Association recommendations for the use of echocardiography in acute cardiovascular care. In this document, we describe the practical applications of echocardiography in patients with acute cardiac conditions, in particular with acute chest pain, acute heart failure, suspected cardiac tamponade, complications of myocardial infarction, acute valvular heart disease including endocarditis, acute disease of the ascending aorta and post-intervention complications. Specific issues regarding echocardiography in other acute cardiac care scenarios are also described.

Layer-Specific Quantification of Myocardial Deformation by Strain Echocardiography May Reveal Significant CAD in Patients With Non–ST-Segment Elevation Acute Coronary Syndrome

OBJECTIVES Our objective was to assess whether patients with significant coronary artery disease (CAD) had reduced endocardial function assessed by layer-specific strain compared with patients without significant CAD. BACKGROUND The left ventricular (LV) wall of the heart comprises 3 myocardial layers. The endocardial layer is most susceptible to ischemic injury. METHODS Seventy-seven patients referred to coronary angiography due to suspected non-ST-segment elevation-acute coronary syndromes (NSTE-ACS) were prospectively included. Coronary occlusion was found in 28, significant stenosis in 21, and no stenosis in 28 patients. Echocardiography was performed 1 to 2 h before angiography. Layer-specific longitudinal and circumferential strains were assessed from endocardium, mid-myocardium, and epicardium by 2-dimensional (2D) speckle-tracking echocardiography (STE). Territorial longitudinal strain (TLS) was calculated based on the perfusion territories of the 3 major coronary arteries in a 16-segment LV model, whereas global circumferential strain (GCS) was averaged from 6 circumferential LV segments in all 3 layers. RESULTS Patients with significant CAD had worse function in all 3 myocardial layers assessed by TLS and GCS compared with patients without significant CAD. Endocardial TLS (mean -14.0 ± 3.3% vs. -19.2 ± 2.2%; p < 0.001) and GCS (mean -19.3 ± 4.0% vs. -24.3 ± 3.4%; p < 0.001) were most affected. The absolute differences between endocardial and epicardial TLS and GCS were lower in patients with significant CAD (Δ2.4 ± 3.6% and Δ6.7 ± 3.8%, respectively) than in those without significant CAD (Δ5.3 ± 2.1% and Δ10.4 ± 3.0%; p < 0.001). This reflects a pronounced decrease in endocardial function in patients with significant CAD. A receiver-operating characteristic curve analysis showed that endocardial and mid-myocardial TLS were superior to identify significant CAD compared with epicardial TLS (p < 0.05), wall motion score index (p < 0.01), and ejection fraction (EF) (p < 0.001). CONCLUSIONS Assessment of layer-specific strain by 2D-STE might identify NSTE-ACS patients with significant CAD. Endocardial function was more affected in patients with significant CAD compared with epicardial function and EF.