Regional Contraction Research Articles

Bending and twisting the embryonic heart: a computational model for c-looping based on realistic geometry.

The morphogenetic process of cardiac looping transforms the straight heart tube into a curved tube that resembles the shape of the future four-chambered heart. Although great progress has been made in identifying the molecular and genetic factors involved in looping, the physical mechanisms that drive this process have remained poorly understood. Recent work, however, has shed new light on this complicated problem. After briefly reviewing the current state of knowledge, we propose a relatively comprehensive hypothesis for the mechanics of the first phase of looping, termed c-looping, as the straight heart tube deforms into a c-shaped tube. According to this hypothesis, differential hypertrophic growth in the myocardium supplies the main forces that cause the heart tube to bend ventrally, while regional growth and cytoskeletal contraction in the omphalomesenteric veins (primitive atria) and compressive loads exerted by the splanchnopleuric membrane drive rightward torsion. A computational model based on realistic embryonic heart geometry is used to test the physical plausibility of this hypothesis. The behavior of the model is in reasonable agreement with available experimental data from control and perturbed embryos, offering support for our hypothesis. The results also suggest, however, that several other mechanisms contribute secondarily to normal looping, and we speculate that these mechanisms play backup roles when looping is perturbed. Finally, some outstanding questions are discussed for future study.

58 Changes in Left Ventricular Force, Velocity and Power Early After CABG

BackgroundA precise understanding and quantification of myocardial contraction is essential for optimising peri-operative care in high risk CABG surgery. Conventional approach has been focused on the magnitude of myocardial contraction,...

WE-G-BRD-07: Investigation of Distal Lung Atelectasis Following Stereotactic Body Radiation Therapy Using Regional Lung Volume Changes Between Pre- and Post- Treatment CT Scans

Purpose: To propose a quantitative method using lung deformations to differentiate between radiation-induced fibrosis and potential airway stenosis with distal atelectasis in patients treated with stereotactic body radiation therapy (SBRT) for lung tumors. Methods: Twenty-four lung patients with large radiation-induced density increases outside the high dose region had their pre- and post-treatment CT scans manually registered. They received SBRT treatments at our institution between 2002 and 2009 in 3 or 5 fractions, to a median total dose of 54Gy (range, 30–60). At least 50 anatomical landmarks inside the lung (airway branches) were paired for the pre- and post-treatment scans to guide the deformable registration of the lung structure, which was then interpolated to the whole lung using splines. Local volume changes between the planning and follow-up scans were calculated using the deformation field Jacobian. Hyperdense regions were classified as atelectatic or fibrotic based on correlations between regional density increases and significant volume contractions compared to the surrounding tissues. Results: Out of 24 patients, only 7 demonstrated a volume contraction that was at least one σ larger than the remaining lung average. Because they did not receive high doses, these shrunk hyperdense regions were likely showing distal atelectasis resulting from radiation-induced airway stenosis rather than conventional fibrosis. On average, the hyperdense regions extended 9.2 cm farther than the GTV contours but not significantly more than 8.6 cm for the other patients (p>0.05), indicating that a large offset between the radiation and hyperdense region centers is not a good surrogate for atelectasis. Conclusion: A method based on the relative comparison of volume changes between different dates was developed to identify potential lung regions experiencing distal atelectasis. Such a tool is essential to study which lung structures need to be avoided to prevent atelectasis and limit lung function loss.

Contrasting magma emplacement mechanisms within the Rogart igneous complex, NW Scotland, record the switch from regional contraction to strike-slip during the Caledonian orogeny

AbstractThe Rogart igneous complex is unique within the northern Scottish Caledonides because it comprises an apparent continuum of magma types that records a progressive change in emplacement mechanisms related to large-scale tectonic controls. Syn-D2 leucogranites and late-D2 quartz monzodiorites were emplaced during crustal thickening and focused within the broad zone of ductile deformation associated with the Naver Thrust. In contrast, emplacement of the post-D2 composite central pluton was controlled by development of a steeply dipping dextral shear zone along the Loch Shin Line, interpreted as an anti-Riedel shear within the Great Glen Fault system. The mantle-derived nature of the late-to-post-D2 melts implies that the Naver Thrust and the Loch Shin Line were both crustal-scale structures along which magmas were channelled during deformation. A U–Pb zircon age of 425±1.5 Ma for the outer component of the central pluton provides an upper limit on regional deformation and metamorphism within host Moine rocks. These findings are consistent with the view that a fundamental change in tectonic regime occurred in the Scottish Caledonides at c. 425 Ma, corresponding to the switch from regional thrusting that resulted from the collision of Baltica and Laurentia, to the development of the orogen-parallel Great Glen Fault system.

Nonuniform surface uplift of the Andean plateau revealed by deuterium isotopes in Miocene volcanic glass from southern Peru

Proposals for rapid late Miocene surface uplift driven by large-scale lithospheric removal beneath the central Andean plateau have been based largely on temperature-sensitive paleoaltimeters. Both the magnitude and mechanism of this proposed pulse of uplift have been challenged. First, climatic general circulation models support protracted uplift with predicted temperature and isotopic shifts enhanced by attainment of threshold elevations. Second, tectonic models in which surface elevations are compensated by regional contraction and crustal thickening question the need for lithospheric removal and predict broadly coeval uplift of the entire plateau. We present hydrogen isotope data using a novel temperature-insensitive volcanic glass proxy from continuous, well-dated lower to middle Miocene basin fill in the Western Cordillera of the northern plateau that show a rapid decrease in δD values (−62.8‰) at 19–16 Ma, with extremely negative values continuing into the Pliocene. We propose that the basin reached its current elevation by 16 Ma, >6 Myr earlier than proposed for the central plateau. The rapid decrease in δD values is consistent with punctuated surface uplift of 2.2–3.7 km between 19 and 16 Ma. Whereas the 3.7 km upper estimate assumes a static climate similar to modern, the 2.2 km lower estimate conservatively incorporates modeled changes in the isotopic composition of precipitation associated with elevation change. Comparison of these results to existing paleoelevation estimates from the Andean plateau facilitates a tentative reconstruction of earliest middle Miocene paleotopography showing a central depression with flanking hinterland and thrust-belt highlands. This apparent pattern of nonuniform plateau uplift contradicts shortening-proportional topographic growth over tens of Myr. We propose that temporally and spatially irregular surface uplift may be linked to pronounced local variability in crustal shortening and/or piecemeal removal of dense mantle lithosphere. Insofar as these irregularities reflect the scale of heterogeneity for surface uplift processes, available paleoelevation estimates point to a principal uplift mechanism that varies over relatively short (<250 km) horizontal distances.

Cardiac resynchronization therapy in a patient with amyloid cardiomyopathy

Summary Cardiac involvement in systemic light chain amyloidosis carries poor prognosis. Amyloid deposition in the myocardium can alter regional left ventricular contraction and cause dyssynchrony. Cardiac resynchronization therapy (CRT) is an eff ective treatment strategy for patients with advanced heart failure and echocardiographic dyssynchrony. We report a clinical and echocardiographic response of a patient with amyloid cardiomyopathy, treated with a combination of chemotherapy and CRT.

Using the palaeontological record of Microtus to test species distribution models and reveal responses to climate change

AbstractAimWe used newly identified fossil specimens to reconstruct the Quaternary distributions of five Microtus species (Rodentia: Arvicolinae) from the Pacific coast of the United States. We used these distributions to test the hypothesis that when projected onto past, alternative climate surfaces, species distribution models (SDMs) created using only climate variables are concordant with the empirical data of fossil Microtus species occurrences.LocationSpecimens from 11 fossil localities in California, Oregon and Nevada were identified and evaluated.MethodsGeometric morphometrics and discriminant analyses were used to identify fossil Microtus specimens. Using a maximum‐entropy modelling approach, the best model for all five species was selected using the Akaike information criterion. Nineteen bioclimate variables were used to create SDMs for the five Microtus species using both Community Climate System Model (CCSM) and Model for Interdisciplinary Research on Climate (MIROC) models.ResultsWe confidently identified 144 Microtus fossils, including the first fossil specimens of Microtus oregoni and Microtus townsendii. SDMs reconstructed approximately half the extralimital fossil occurrences (i.e. those found outside the present‐day range). Those species with extralimital occurrences not reconstructed have niche models primarily influenced by precipitation variables. The two species whose extralimitals were well predicted occupy indistinguishable climatic niches.Main conclusionsThe ranges of Pacific coast Microtus species have undergone substantial regional contractions since the Last Glacial Maximum (LGM; 21 ka). Inconsistencies between LGM SDMs and Quaternary fossil ranges indicate potential problems with LGM precipitation reconstructions, although interspecific interactions are also likely to contribute to these differences. Overall, the study highlights the need for further, detailed, species‐level palaeodistributions to put recent observations in a broader temporal context and examine the effectiveness of SDMs coupled with climate models for predicting range dynamics under scenarios of climate change.

Radial Strain Delay Based on Segmental Timing and Strain Amplitude Predicts Left Ventricular Reverse Remodeling and Survival After Cardiac Resynchronization Therapy

Dyssynchrony assessment based on the timing of regional contraction is inherently independent of underlying myocardial contractility. We tested the hypothesis that patient selection for cardiac resynchronization therapy (CRT) would be enhanced using a parameter derived from the net radial strain delay (RSD) for the 12 basal and mid-left ventricular segments (calculated radial strain delay RSD [RSDc]), based on not only timing but also amplitude of segmental strain. Echocardiographic data were analyzed in 240 patients with symptomatic heart failure undergoing CRT (New York Heart Association class III/IV; QRS >120 milliseconds; ejection fraction, 23±7%). RSDc was calculated as the sum of difference between peak radial strain and radial strain at aortic valve closure before CRT implantation. CRT response was defined as >15% reduction in left ventricular end-systolic volume at 6 months. In a derivation group (n=102), RSDc was higher in responders compared with nonresponders (74±39% versus 29±15%; P<0.001) and related to the change in left ventricular end-systolic volume (r=-0.53; P<0.001). RSDc >40% predicted remodeling (sensitivity, 87%; specificity, 88%). In the validation group (n=108), RSDc similarly predicted response (sensitivity, 89%; specificity, 84%). Survival at long-term follow-up was greater in patients with RSDc >40% (P<0.0001). RSDc, based on both the timing and the amplitude of segmental strain, has a strong predictive value for CRT remodeling response and long-term survival.

Early foreland deformation of the Fuegian Andes (Argentina): Constraints from the strain analysis of Upper Cretaceous-Danian sedimentary rocks

This contribution addresses new structural data from Upper Cretaceous-Danian sedimentary rocks of the Fuegian Andes orogenic front in Argentina. The structures studied, called D′, were formed during the early foreland deformation of the orogen, in the Late Cretaceous-Danian, in times when South America and Antarctica were still connected. The strain analysis of these structures indicates that deformation occurred at upper-crustal depths, and was characterized by flexural folding accompanied by formation of pressure-solution tectonic foliations in zones of higher strain. Deformation intensities increase toward the hinterland and with depth. The history of deformation involved progression from layer-parallel shortening to folding above a detachment, and further formation of a forward-propagating thrust wedge. Layer-parallel shortening and incipient folding recorded in Maastrichtian-Danian rocks indicate the leading edge of D′ deformation. Non-coaxial finite strain orientations were involved during formation of D′ structures along the Fuegian Andes front. These finite strain orientations cannot be explained with the SW-NE regional contraction usually assumed to have driven Andean deformation in this region; alternatively, we consider that N-S contraction combined with buttressing against the cratonic foreland comprise a more suitable interpretation for D′ and younger deformation.

Left Ventricular Activation Imaging by 3-Dimensional Speckle-Tracking Echocardiography

Activation imaging with 3-dimensional speckle-tracking echocardiography (3D-STE) aims to visualize the time required for the onset of regional contraction from QRS onset. We hypothesized that the optimal setting of activation imaging was associated with electrical activation. This study was designed to determine an optimal setting of activation imaging with 3D-STE in comparison with that of a voltage mapping system and to assess the feasibility of this imaging method. We enrolled 7 patients who underwent electrical voltage mapping. Regional deformation was measured by area change ratio (ACR) with 3D-STE. Activation imaging data were obtained at 10%, 25%, 50%, and 100% of maximal ACR values as the threshold for onset of regional contraction. Duration of LV electrical intraventricular activation time (IVAT(electrical)) by voltage mapping and mechanical IVAT (IVAT(mechanical)) by activation imaging was defined as the time difference between the first and latest endocardial activation sites. We obtained 21 data sets under various conduction patterns and pacing configurations. The strongest correlation between IVAT(mechanical) and IVAT(electrical) was observed at 25% of maximal ACR values (IVAT(electrical)=0.47 * IVAT(mechanical)+20, R=0.80, P<0.001). Concordance of the first and latest activated segments between activation imaging and voltage mapping was 90.5% at this setting (19 studies). Activation imaging with 3D-STE may be a feasible noninvasive method of dyssynchrony imaging based on electromechanical coupling.

Application of 3-Dimensional Speckle Tracking Imaging to the Assessment of Right Ventricular Regional Deformation

The aim of this study was to carry out 3-dimensional speckle tracking imaging (3DSTI) of the right ventricle (RV) and evaluate RV regional wall deformation. 3DSTI of the RV was performed in 35 normal subjects, 8 patients with arrhythmogenic right ventricular cardiomyopathy, and 8 patients with pulmonary arterial hypertension. Peak systolic area change ratio and regional contraction timing relative to global systolic time (time to peak strain/time to end-systole×100) were measured in each segment. Good-quality images were acquired of the inflow segment in 87%, apex in 87%, outflow in 57%, and septum in 94% of the 35 normal subjects. In normal subjects, peak systolic area change ratio of the inflow anterior wall was -41±14%; inflow inferior wall, -35±9%; apical anterior wall, -41±10%; apical inferior wall, -31±11%; outflow, -31±9%; and septum wall, -36±11%. Contraction timing of the apical anterior wall and septum wall were earlier than those of other segments. In patients with RV dysfunction, 3DSTI indicated low peak systolic area change ratio in the damaged area. RV 3DSTI indicated segmental heterogeneity in magnitude and timing of RV contraction. 3DSTI may be a promising modality for providing precise quantitative information on complex RV wall motion.

Evaluation of chronic ischemic heart disease with myocardial perfusion and regional contraction analysis by contrast-enhanced 256-MSCT

To investigate myocardial viability in chronic ischemic heart disease by myocardial perfusion and regional contraction analysis using 256-slice MSCT coronary angiography (CCTA). In 30 patients with prior myocardial infarction (MI), CCTA with retrospective ECG-gating and stress-redistribution thallium-201 SPECT were performed. Using the same raw data as used for CCTA, myocardial perfusion imaging (CT-MPI) was reconstructed at four phases during the cardiac cycle. Mean myocardial attenuation and wall thickness at end-systole and end-diastole were measured in the MI areas depicted by SPECT, and they were compared between viable and non-viable segments categorized by SPECT. End-systolic thickness was significantly greater for viable than for non-viable segments (12.0 ± 3.2 vs. 9.6 ± 3.5 mm, p = 0.0017). There was no difference in end-diastolic thickness. Myocardial attenuation was significantly higher for viable than for non-viable segments in the subendocardium (62 ± 13 vs. 70 ± 11 HU, p = 0.003) and the epicardium (65 ± 13 vs. 80 ± 15 HU, p = 0.0002). The systolic wall thinning and epicardial low-attenuation areas were the indicative findings of CT-MPI for non-viable segments in the prior MI.

Improvement in Coronary Blood Flow Velocity With Acute Biventricular Pacing Is Predominantly Due to an Increase in a Diastolic Backward-Travelling Decompression (Suction) Wave

Normal coronary blood flow is principally determined by a backward-traveling decompression (suction) wave in diastole. Dyssynchronous chronic heart failure may attenuate suction, because regional relaxation and contraction overlap in timing. We hypothesized that biventricular pacing, by restoring left ventricular (LV) synchronization and improving LV relaxation, might increase this suction wave, improving coronary flow. Ten patients with chronic heart failure (9 males; age 65±12; ejection fraction 26±7%) with left bundle-branch block (LBBB; QRS duration 174±18 ms) were atriobiventricularly paced at 100 bpm. LV pressure was measured and wave intensity calculated from invasive coronary flow velocity and pressure, with native conduction (LBBB) and during biventricular pacing at atrioventricular (AV) delays of 40 ms, 120 ms, and separately preidentified hemodynamically optimal AV delay. In comparison with LBBB, biventricular pacing at separately preidentified hemodynamically optimal AV delay (BiV-Opt) enhanced coronary flow velocity time integral by 15% (7%-25%) (P=0.007), LV dP/dt(max) by 15% (10%-21%) (P=0.005), and (neg)dP/dt(max) by 17% (9%-22%) (P=0.005). The cumulative intensity of the diastolic backward decompression (suction) wave increased by 26% (18%-54%) (P=0.005). The majority of the increase in coronary flow velocity time integral occurred in diastole (69% [41%-84% ]; P=0.047). The systolic compression waves also increased: forward by 36% (6%-49%) (P=0.022) and backward by 38% (20%-55%) (P=0.022). Biventricular pacing at AV delays of 120 ms generated a smaller LV dP/dt(max) (by 12% [5%-23% ], P=0.013) and (neg)dP/dt(max) (by 15% [8%-40% ]; P=0.009) increase than BiV-Opt, against LBBB as reference; BiV-Opt and biventricular pacing at AV delays of 120 ms were not significantly different in coronary flow velocity time integral or waves. Biventricular pacing at AV delays of 40 ms was no different from LBBB. When biventricular pacing improves LV contraction and relaxation, it increases coronary blood flow velocity, predominantly by increasing the dominant diastolic backward decompression (suction) wave.

Methodology for Jointly Assessing Myocardial Infarct Extent and Regional Contraction in 3-D CMRI

Automated extraction of quantitative parameters from cardiac magnetic resonance images is crucial for the management of patients with myocardial infarct. This paper proposes a postprocessing procedure to jointly analyze Cine and delayed-enhanced (DE) acquisitions, in order to provide an automatic quantification of myocardial contraction and enhancement parameters and a study of their relationship. For that purpose, the following processes are performed: 1) DE/Cine temporal synchronization and 3-D scan alignment, 2) 3-D DE/Cine rigid registration in a region about the heart, 3) myocardium segmentation on Cine-MRI and superimposition of the epicardial and endocardial contours on the DE images, 4) quantification of the myocardial infarct extent (MIE), 5) study of the regional contractile function using a new index, the amplitude to time ratio (ATR). The whole procedure was applied to ten patients with clinically proven myocardial infarction. The comparison between the MIE and the visually assessed regional function scores demonstrated that the MIE is highly related to the severity of the wall motion abnormality. In addition, it was shown that the newly developed regional myocardial contraction parameter (ATR) decreases significantly in delayed enhanced regions. This largely automated approach enables the combined study of regional MIE and left ventricular function.

Geophysical and structural pattern of the Knížecí Stolec pluton and its host rocks in the south-western part of the Moldanubian Zone, Bohemian Massif

*Corresponding author A detailed airborne magnetic and gamma-ray spectrometric as well as ground gravity survey in the south-western part of the Moldanubian Zone (Bohemian Massif) provided detailed geophysical characteristics of the principal geological units and large-scale tectonic features. The Knižeci Stolec durbachitic pluton with high contents of natural radioactive elements (Th, U and K) represents a body with no magnetically anomalous response but a pronounced positive gravity anomaly. The Křisťanov granulite massif, which is a host rock of the Knižeci Stolec pluton, exhibits low concentrations of Th and U, high abundances of K, slight magnetic and a negative gravity anomalies. The Plechý composite pluton is characterized by strikingly low gravity and an extremely monotonous magnetic field. One of its petrographic varieties (the Třistolicnik granite) is enriched in natural radioactive elements, especially in Th and U. Metamorphic complexes of the Monotonous and Varied groups contain multiple magnetic anomalies mostly related to the intercalated metabasic rocks; they also cause positive gravity anomalies. The Linsser density boundaries at a depth of 0.5 km clearly delimit the Plechý composite pluton and the Lhenice zone and indicate several structurally and/or lithologically different domains within the Křisťanov granulite massif and in the Knižeci Stolec pluton. The 2.5D gravity model indicates an asymmetric shape of the Knižeci Stolec pluton, which is deepest in its SE part (at least 4 km). The joint interpretation of the geophysical and structural data revealed that the maximum depth of the pluton is c. 4.5 km, with gently to moderately dipping intrusive contacts in the north and subvertical orientation in the south. The asymmetric shape of the pluton is consistent with its inferred syn-tectonic emplacement coeval with the regional subvertical contraction and development of regional flat-lying fabric. The gravity model combined with structural analyses also implies a considerable depth of the south Bohemian granulite massifs. This indicates their steep exhumation path and is at variance with the model of the Moldanubian Zone as a sequence of flat-lying nappes. The south-western part of the studied area is reworked by the NE-directed compression, referred to as the ‛Bavarian’ deformation phase.

006 Improvement in coronary blood flow with acute biventricular pacing is predominantly due to an increase in a diastolic backward-travelling decompression (suction) wave

BackgroundNormal coronary blood flow is principally determined by a backward-travelling decompression (suction) wave in diastole. This wave may be attenuated in chronic heart failure, reducing blood flow, as regional relaxation...

Inverted McConnell Sign

There is a well-recognized echocardiographic pattern of the right ventricle (RV) wall motion reported by McConnell which is characterized by normokinesia of the apical segment and akinesia of the mid–free wall with persistence of abnormal wall motion at the base. We describe a case of an 85-year-old man with acute massive bilateral pulmonary embolism with opposite regional contraction pattern of the RV free wall than the one referred by McConnell consisting of hyperkinesia of the basal RV free wall and akinesia of the mid-RV free wall and RV apex, a finding that could be called “inverted McConnell sign.”

Evaluation of regional work from ECG-gated SPECT images through solution of equations of continuity for fluids--mechanical cardiac work calculated using thin wall model

Regional contraction work (RCW) of left ventricle (LV) was evaluated from cardiac perfusion images of ECG-gated single photon emission computed tomography (ECG-SPECT). The mechanical work was computed as a product of force and displaced distance. Force was determined from Laplace's law under a rectangle pressure. Deformation of wireframe representing LV was calculated from equations of continuity for two-dimensional fluids. Experiments were performed with homemade life-sized cardiac models. Total contraction work (TCW) and stroke work (SW) were 524.0 ± 166.1 mJ/beat and 709.8 ± 169.5 mJ/beat, respectively, in normal subjects (n = 23). Moderate correlation was seen between TCW and SW (y = −43.4 + 0.779 x, r = 0.815). The regional contraction amplitude (RCA), synchronous contraction index and RCW were 35.4 ± 3.5%, 95.4 ± 3.1% and 5.58 ± 0.97 mJ cm−2/beat in normal subjects, whereas those in patients with decreased ejection raction (EF) ≤ 30% (n = 6) were 19.6 ± 7.7%, 64.4 ± 32.2% and 2.58 ± 0.82 mJ cm−2/beat (p < 0.0001, Student's t-test). There was a poor correlation between RCW and RCA (y = 1.648 ± 0.116 x, r = 0.501) in normal subjects, suggesting that it might not be suitable to use RCA as an alternative to evaluate RCW.

A new interpretation of deformation rates in the Snake River Plain and adjacent basin and range regions based on GPS measurements

We evaluate horizontal Global Positioning System (GPS) velocities together with geologic, volcanic, and seismic data to interpret extension, shear, and contraction within the Snake River Plain and the Northern Basin and Range Province, U.S.A. We estimate horizontal surface velocities using GPS data collected at 385 sites from 1994 to 2009 and present an updated velocity field within the Stable North American Reference Frame (SNARF). Our results show an ENE-oriented extensional strain rate of 5.9 {+-} 0.7 x 10{sup -9} yr{sup -1} in the Centennial Tectonic belt and an E-oriented extensional strain rate of 6.2 {+-} 0.3 x 10{sup -9} yr{sup -1} in the Intermountain Seismic belt combined with the northern Great Basin. These extensional strain rates contrast with the regional north-south contraction of -2.6 {+-} 1.1 x 10{sup -9} yr{sup -1} calculated in the Snake River Plain and Owyhee-Oregon Plateau over a 125 x 650 km region. Tests that include dike-opening reveal that rapid extension by dike intrusion in volcanic rift zones does not occur in the Snake River Plain at present. This slow internal deformation in the Snake River Plain is in contrast to the rapidly-extending adjacent Basin and Range provinces and implies shear along boundaries of the Snakemore » River Plain. We estimate right-lateral shear with slip rates of 0.5-1.5 mm/yr along the northwestern boundary adjacent to the Centennial Tectonic belt and left-lateral oblique extension with slip rates of 10{sup 6} yrs, the low-strain field in the Snake River Plain and Owyhee-Oregon Plateau would extend through the Quaternary.« less

Efficacy of Longitudinal Speckle Tracking Strain in Conjunction with Isometric Handgrip Stress Test for Detection of Ischemic Myocardial Segments

Isometric handgrip stress test is a simple method for detecting coronary artery disease (CAD). However, the value of this method alone is limited by relatively low sensitivity. This study thus aimed to investigate the usefulness of two-dimensional speckle-tracking strain combined with handgrip for CAD patients. We studied 35 patients with stable angina pectoris who underwent percutaneous coronary intervention (PCI). Longitudinal (L-ɛ) and transverse peak systolic (T-ɛ) strains were measured from three standard apical views before and 1 month after PCI. Segments corresponded to perfusion territories of coronary arteries were divided into two groups based on coronary angiography results: stenotic (S) and nonstenotic (NS) segment. L-ɛ in S segments increased significantly after PCI, from -15.8% to -17.6% (P < 0.01), but not in NS segments. Moreover, L-ɛ in S segments increased significantly during handgrip before PCI, from -15.8% to -17.6% (P < 0.01), but decreased after PCI, from -17.6% to -16.7% (P = 0.02). In contrast, L-ɛ in NS segments decreased significantly during the isometric handgrip stress test before and after PCI (P < 0.05). Especially noteworthy is that a relative change in L-ɛ of >1.2% during handgrip before PCI could detect significant coronary stenosis with a sensitivity of 80%, specificity of 66%, and area under the curve of 0.77 (P < 0.001). On the other hand, no significant changes were observed in either T-ɛ segments during handgrip either before or after PCI. Longitudinal speckle-tracking strain combined with handgrip may constitute a valuable tool for detection of ischemic myocardial segments and prediction of improvement of regional contraction after revascularization.