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Biomedical subjects

George R Sutherland

Publications and source records attributed to George R Sutherland.

At least 37 records · Page 2Linked to original sources
PubMed2003

Identification of acutely ischemic myocardium using ultrasonic strain measurements. A clinical study in patients undergoing coronary angioplasty.

OBJECTIVES: The goal of this study was to investigate whether the changes in myocardial deformation measured with ultrasonic strain could accurately identify acutely ischemic myocardium during coronary angioplasty. BACKGROUND: Early identification of acute myocardial ischemia has important clinical implications. The accuracy of ultrasonic strain for the detection of acute myocardial ischemia has been validated in animal experiments but has not been investigated in the clinical setting. METHODS: In 73 patients (64 +/- 12 years), either radial or longitudinal strain values were monitored in the "at-risk" segments before, during, and early after right, circumflex, and left anterior descending coronary angioplasty. Based on the visual wall motion assessed before the angioplasty, segments were divided into normokinetic (group I) and hypo/akinetic (group II). Strain data in the "at-risk " segments were compared with values derived from the adjacent nonischemic segments and normal values in 20 controls. RESULTS: Coronary occlusion induced a marked reduction in the systolic strain both in the radial (from 49 +/- 6.9% to 23 +/- 4.6% in group I and from 21.9 +/- 11% to 11.3 +/- 8.4% in group II, p < 0.001) and longitudinal directions. Concomitantly, postsystolic strain increased (from 3.8 +/- 3.1% to 14.6 +/- 9.5% in group I, and from 4.4 +/- 3.7% to 11.3 +/- 7.8% in group II in radial direction, p < 0.001). Upon reperfusion, all deformation parameters returned to near preocclusion values. In comparison with control, baseline, and reperfusion data, the systolic and postsystolic strain parameters measured during total coronary occlusion identified acutely ischemic myocardium with a sensitivity of 86% to 95% and a specificity of 83% to 89%. CONCLUSIONS: In this model of acute ischemia, ultrasonic strain indexes differentiate acutely ischemic segments from both normal and dysfunctional myocardium. This should be a promising new approach to the bedside monitoring of acute ischemic changes in regional myocardial function.

Acute Disease↗
PubMed2003

Defining the transmurality of a chronic myocardial infarction by ultrasonic strain-rate imaging: implications for identifying intramural viability: an experimental study.

BACKGROUND: In a correlative functional/histopathologic study, we investigated the regional deformation characteristics of both chronic nontransmural and transmural infarctions before and after a dobutamine challenge. METHODS AND RESULTS: After stenosing copper-coated stent implantation to produce circumflex artery endothelial proliferation, 18 pigs were followed up for 5 weeks. Posteuthanasia histology showed 10 to have a nontransmural and 8 a transmural infarction. Eight nonstented animals served as controls. Regional radial function was monitored by measuring ultrasound-derived peak systolic strain rates (SR(SYS)) and systolic strains (epsilon(SYS)) (1) before stent implantation and (2) at 5 weeks, at baseline (bs) and during an incremental dobutamine infusion. In controls, dobutamine induced a linear increase in SR(SYS) (dobutamine: bs, 4.8+/-0.4 s(-1); 20 microg x kg(-1) x min(-1), 9.9+/-0.7 s(-1); P<0.0001) and an initial increase of epsilon(SYS) at low dose (bs, 58+/-5%; at 5 microg x kg(-1) x min(-1), 78+/-6%; P<0.05) but a subsequent decrease during higher infusion rates. In the nontransmural group, bs SR(SYS) and epsilon(SYS) were significantly lower than prestent values (SR(SYS), 2.9+/-0.5 s(-1) and epsilon(SYS), 32+/-6%, P<0.05 versus prestent). During dobutamine infusion, SR(SYS) increased slightly at 5 microg x kg(-1) x min(-1) (4.7+/-0.6 s(-1), P<0.05) but fell during higher infusion rates, whereas epsilon(SYS) showed no change. For nontransmural infarctions, transmural scar extension correlated closely with epsilon(SYS) at bs (r=0.88). For transmural infarctions, SR(SYS) at bs was significantly reduced and epsilon(SYS) was almost not measurable (SR(SYS), 1.8+/-0.3 s(-1); epsilon(SYS), 3+/-4%). Both deformation parameters showed no further change during the incremental dobutamine infusion. CONCLUSIONS: Ultrasonic deformation values could clearly differentiate chronic nontransmural from transmural myocardial infarction. The transmural extension of the scar could be defined by the regional deformation response.

Animals↗
PubMed2003

One-dimensional ultrasonic strain and strain rate imaging: a new approach to the quantitation of regional myocardial function in patients with aortic stenosis.

Abnormalities in regional left ventricular (LV) function in aortic stenosis (AS) have yet to be appropriately characterized. One-dimensional strain (epsilon) and strain rate imaging (SRI), new ultrasound (US) indices for quantifying regional wall deformation, might allow this. The aims of this study were 1. to define regional radial and longitudinal epsilon /SR in AS; 2. to establish if they are related to the severity of the disease; and 3. to determine if regional deformation is further altered by coexistent coronary artery disease (CAD). A total of 40 patients were studied: Group I with isolated AS (10 women, 10 men; mean age 66 years) and group II with AS and concomitant CAD (CAD/AS) (13 women, 7 men, mean age 68 years). Data were compared to 20 age-matched healthy people (N). Regional systolic maximal velocity/SR and end-systolic and maximal epsilon were measured. The maximal systolic velocity/SR in AS and CAD/AS patients were significantly reduced compared to N. The two patient groups could be further differentiated by end-systolic and maximal epsilon, which demonstrated a further reduction in both epsilon indices in CAD/AS (i.e., maximal radial epsilon 29.3%, AS; 23.7%, CAD/AS; 40.4%, N; AS and CAD/AS vs. N, AS vs. CAD/AS, p < 0.05). Indices of radial and longitudinal deformation correlated both with aortic valve area (AVA) and stroke volume (SV) (i.e., radial maximal epsilon and AVA, r = 0.77, p < 0.05). A significant correlation was also found between epsilon indices and the severity of left anterior descending (LAD) or circumflex artery (CX) coronary artery. Regional myocardial deformation in AS is abnormal. In the absence of CAD, the degree of abnormality correlates with aortic valve area (AVA). The severity of the disease was best expressed by changes in regional epsilon. In CAD/AS patients, there was a significant further reduction in end-systolic and maximal epsilon. These changes correlated with the severity of coronary narrowing in the subtending vessel.

Adult↗
PubMed2003

Can regional strain and strain rate measurement be performed during both dobutamine and exercise echocardiography, and do regional deformation responses differ with different forms of stress testing?

BACKGROUND: Regional strain (epsilon) and strain rate (SR) measurement could be the optimal approach to quantifying stress echocardiography images. However, signal noise could preclude their use. Study aims Our aim was to compare the feasibility of regional peak systolic (p) velocity (Vel), pSR/epsilon measurement, and their normal responses during upright (group 1, n = 10) and supine (group 2, n = 10) bicycle exercise and (group 3, n = 10) dobutamine stress. METHODS: For each type of stress study, pVel/pSR/epsilon data were acquired at baseline, low (100-120 bpm), and peak (140-160 bpm) heart rate (HR); and during recovery. RESULTS: During dobutamine pVel/pSR/epsilon were interpretable in >95% of segments at every stress stage, whereas in groups 1 and 2 pSR/epsilon responses were noninterpretable in >36% of segments (P <.0002). The highest proportions of data exclusions were from the lateral and anterior walls. In all groups, regional systolic pVel and SR values increased linearly and reached maximal value at peak HR (P <.0006 vs baseline). Pepsilon showed a biphasic response, initially increasing at low HR, and then remaining constant or falling at peak HR. CONCLUSION: PSR/pepsilon quantification of stress echocardiography may currently be restricted to dobutamine as increased signal noise precludes adequate data acquisition during exercise. For all forms of stress both pSR and pVel increased linearly, whereas pepsilon response was biphasic as a result of the reduced filling at higher HRs.

Adult↗
PubMed2003

Differential changes in regional right ventricular function before and after a bilateral lung transplantation: an ultrasonic strain and strain rate study.

The evaluation of regional right ventricular function by ultrasound remains a challenge. This case report demonstrates the potential value of the new cardiac deformation indices, strain and strain rate imaging, in determining the differing regional abnormalities in longitudinal right ventricular function before and after bilateral lung transplantation. These indices were measured in a patient with severe right ventricular dysfunction as a result of primary pulmonary hypertension.

Adult↗
PubMed2003

Restrictive left ventricular filling in hypereosinophilic syndrome as a result of partial cavity obliteration by an apical mass: a strain/strain rate study.

We present a case of hypereosinophilic syndrome with a large apical mass, which markedly reduced end-systolic left ventricular cavity volume. Standard blood pool Doppler findings showed a restrictive filling pattern. However, ultrasound-derived regional strain rate and strain parameters suggested that wall deformation was not compromised, inferring that the restrictive filling pattern in this case was solely as a result of the reduction in end-systolic cavity size.

Blood Flow Velocity↗
PubMed2003

[A new echocardiographic approach to evaluate myocardial function in congenital cardiopathies: strain and strain rate imaging].

Based on color Doppler methodology, regional myocardial strain rates and strain can now be calculated by comparing local myocardial velocity profiles. These deformation data sets may be an important new approach to quantifying regional function of the left or right ventricle in congenital heart disease. This review will give an introduction to the principles behind the technique and how data are acquired and processed. It will also discuss the findings of clinical studies based on this new technique.

Echocardiography, Doppler, Color↗
PubMed2002

Quantification of regional right and left ventricular function by ultrasonic strain rate and strain indexes after surgical repair of tetralogy of Fallot.

The quantification of regional myocardial function in tetralogy of Fallot (TOF) by conventional M-mode and 2-dimensional echocardiography is difficult because of the complex right ventricular (RV) and altered left ventricular (LV) geometry. In 30 asymptomatic postoperative TOF patients (aged 4 to 16 years) with a low pressure in the right ventricle and with varying degrees of pulmonary regurgitation and in 30 aged-matched healthy children, the ultrasonic-derived regional deformation parameters peak systolic strain rate (SR) and systolic strain (epsilon) were acquired from ventricles and compared. In TOF RV free walls, SR, and epsilon were reduced in the basal, mid-, and apical segments and averaged -1.5 +/- 0.6 second(-1) for SR and -22 +/- 8% for epsilon, respectively (p <0.001 vs normals). Peak systolic SR of the basal RV free wall correlated significantly with the QRS duration of the electrocardiogram (r = 0.81, p <0.0001). Abnormalities in RV deformation were more marked in patients with transannular patches versus infundibular patches. In the septum there was a homogeneous reduction in SR and epsilon in the basal, mid-, and apical segments. These averaged -1.4 +/- 0.3 second(-1) for SR and -19 +/- 4% for epsilon, respectively (p <0.01 vs normals). Longitudinal SR and epsilon values of the 3 LV lateral wall segments (averaged SR = -1.6 +/- 0.4 second(-1), averaged epsilon = -20 +/- 5%; p <0.05 vs normals), and radial SR and epsilon of the LV posterior wall (SR = 3.3 +/- 0.9 second(-1); epsilon = 51 +/- 14%; p <0.05 vs normals) were significantly reduced. Thus, abnormalities in regional RV and LV systolic myocardial function in asymptomatic postoperative TOF patients were quantified by the deformation parameters SR and epsilon. RV deformation abnormalities are associated with electrical depolarization abnormalities.

Adolescent↗
PubMed2002

Assessment of accessory atrioventricular pathways by Doppler myocardial imaging.

PURPOSE: The use of electrophysiologic studies (EPS) for the localization of accessory atrioventricular connections in Wolff-Parkinson-White syndrome (WPW) requires accurate evaluation of the site of bypass tract insertion. Doppler myocardial imaging (DMI) is a new ultrasound technique that allows the detection of abnormal and early regional myocardial depolarization. The purpose of this study was to identify an abnormal pathway site in WPW patients. METHODS: Twenty-one patients with ventricular preexcitation were studied by DMI. Two-dimensional color DMI, velocity maps, acceleration maps, and pulsed-wave applications were used. A subsequent diagnostic EPS was performed. The results of EPS were taken as the gold standard diagnostic procedure. Radiofrequency catheter ablation therapy was then performed on all patients. RESULTS: The anomalous pathway was detected by DMI in 16 (76%) of 21 patients (9 [90%] of 10 with left pathways and 7 [64%] of 11 with right pathways), with respect to results of the EPS. Pathway detection was better with pulsed-wave DMI (76%) with its higher temporal resolution as compared with M-mode velocity map (57%) and acceleration map (47%). In most of the patients with successful radiofrequency ablation, an immediate resolution of the abnormal ventricular depolarization occurred and was detectable by DMI. CONCLUSIONS: Our findings demonstrate the feasibility of DMI to assess the early ventricular contraction associated with atrioventricular accessory pathways. Therefore, DMI appears to be a clinically useful adjunct to noninvasive evaluation of abnormal myocardial depolarization in WPW and to evaluate the results after radiofrequency ablation, even though its accuracy is considerably better for left-sided accessory pathways than for right-sided ones.

Adult↗
PubMed2002

Acute changes in systolic and diastolic events during clinical coronary angioplasty: a comparison of regional velocity, strain rate, and strain measurement.

Ultrasound-derived natural strain rate and strain are new Doppler myocardial imaging (DMI) parameters, which can measure local deformation independently of overall heart motion and thus could better characterize local contractility than DMI velocities alone. This study was undertaken to evaluate the relative benefits of regional velocity, strain rate, and strain measurements in detecting the range of acute changes in regional myocardial function in the "at-risk" zone during coronary angioplasty. Sixty-one patients (aged 63 +/- 12, 18 women) with stable angina pectoris were studied before, at the end of, and during recovery from a 60-second percutaneous transluminal coronary angioplasty (PTCA) balloon occlusion. High frame rate (147 fps) color DMI regional velocity data were derived from basal posterior (parasternal view) and mid, apical septal (apical view) "at-risk" segments as well as from the corresponding segments in healthy subjects and analyzed offline for velocity (VEL), strain rate (SR), and strain (epsilon) measurements. Coronary occlusion resulted in the reduction in VEL(SYS), SR(SYS), and epsilon(SYS) values for both radial (RCA/CX occlusion) and longitudinal data (LAD occlusion) in all segments analyzed. Velocity parameters alone failed to distinguish between baseline and occlusive measurements in the "at-risk" segments with visually abnormal baseline function. SR(SYS) and epsilon(SYS) had a higher diagnostic accuracy (sensitivity 75%, 80% and specificity 80%, 82%, respectively) than VEL(SYS) velocity alone (sensitivity 68%, specificity 65%,) for identifying acute ischemia in either baseline normal and abnormal segments. DMI-derived indexes can identify and quantify the spectrum of acute systolic and diastolic ischemic changes induced during clinical PTCA. The quantitation of regional deformation rather than motion would appear to be more appropriate in detecting and quantifying acute ischemic changes in myocardial function, especially in segments with pre-existing abnormal function.

Adult↗
PubMed2002

Quantification of regional left and right ventricular radial and longitudinal function in healthy children using ultrasound-based strain rate and strain imaging.

BACKGROUND: Noninvasive assessment of left (LV) and right (RV) ventricular function in children could benefit from a technique that would characterize local myocardial deformation. Color Doppler myocardial imaging (CDMI) allows the calculation of either local longitudinal or radial Strain Rate (SR) and Strain (epsilon). To determine the clinical feasibility and reproducibility of longitudinal and radial SR and epsilon, the following study was carried out. METHODS: CDMI data were obtained from 33 healthy children (4-16 years). To quantify regional longitudinal and radial function SR and epsilon data were obtained from apical and parasternal views respectively. From the extracted SR curves, peak values for systole, early diastole, and late diastole were calculated. From the extracted epsilon curves the systolic, early and late diastolic epsilon values were calculated. RESULTS: LV longitudinal deformation were homogeneous for LV basal, mid and apical segments (peak systolic SR: -1.9 +/- 0.7 s(-1), systolic epsilon -25% +/- 7%). Longitudinal SR and epsilon values were significantly higher and heterogeneous in the RV (compared with LV walls) and were maximal in the mid part of the RV free wall (peak systolic SR: -2.8 +/- 0.7 s(-1), systolic epsilon -45% +/- 13%). The RV inferior wall showed homogeneous but lower longitudinal SR and epsilon values. The LV systolic and diastolic SR and epsilon values were higher for deformation in the radial direction compared with the longitudinal direction (radial peak systolic SR: 3.7 +/- 0.9 s(-1), radial systolic epsilon 57% +/- 11%; P <.0001). The interobserver variability for radial systolic epsilon and SR was 10.3% and 13.1%, respectively. CONCLUSION: Ultrasound-based Strain SR/epsilon imaging is a practical, reproducible clinical technique, which allows the calculation of regional longitudinal and radial deformation from both LV and RV segments. The combination of regional SR/epsilon indices and the timing of specific systolic or diastolic regional events may offer a new noninvasive approach to quantifying regional myocardial function in congenital and acquired heart disease in children.

Adolescent↗
PubMed2002

Can strain rate and strain quantify changes in regional systolic function during dobutamine infusion, B-blockade, and atrial pacing--implications for quantitative stress echocardiography.

BACKGROUND: We investigated the ability of ultrasonic strain rate (SR) and strain (epsilon) to quantify the changes in normal myocardial function at varying inotropic states and heart rates (HR) in an attempt to determine whether these new regional function indices are potentially robust enough to quantitate stress echocardiography. METHODS AND RESULTS: Twenty closed-chest pigs underwent incremental atrial pacing (AP: 120-180/min, n = 7), dobutamine infusion (DI: 2.5-20 microg/kg/min, n = 7) or esmolol infusion with subsequent pacing (EI: 0.5 +/- 0.15 mg/kg/min with pacing 120-180/min, n = 6). Radial deformation of the left ventricular posterior wall was interrogated using the parasternal short-axis view to derive regional systolic SR and epsilon values. At baseline SR and epsilon averaged 5.0 +/- 0.4 s(-1) and 60% +/- 4%, respectively. SR remained unchanged during AP and increased linearly with DI (at 2.5 microg/kg/min = 6.2 +/- 0.3 s(-1), P <.05 vs baseline; at 20 microg/kg/min = 9.9 +/- 0.7 s(-1), P <.0001 vs baseline), whereas EI resulted in a constant decrease of 30% +/- 4% in SR (P <.05). SR and left ventricular dP/dt(MAX) correlated linearly over the induced change in inotropic states and HR (r = 0.82; P <.0001). Conversely, epsilon values decreased during AP (at 180/min = 36% +/- 2%, P <.001). During DI, epsilon initially increased at 2.5 and 5 microg/kg/min (at 5 microg/kg/min = 77% +/- 6%, P <.05) and decreased for higher doses because of increasing HR. EI resulted in a decrease of 30% +/- 4% in epsilon with a further decrease during subsequent pacing. epsilon correlated linearly with left ventricular ejection fraction (r = 0.87; P <.0001). CONCLUSION: Both SR and epsilon can quantify the changes in myocardial function during a range of inotropic challenges and over the range of physiologic HRs encountered during clinical stress echocardiography. SR may reflect regional contractile function, whereas epsilon reflects changes in ventricular geometry. This study would suggest that for quantitative stress echocardiography SR is better in quantification of changes in contractile function being relatively independent of HR.

Adrenergic beta-Antagonists↗
PubMed2002

Strain rate imaging for the assessment of preload-dependent changes in regional left ventricular diastolic longitudinal function.

BACKGROUND: Strain rate imaging is a new and intriguing way of displaying myocardial deformation properties by means of echocardiography. With high frame rate strain rate imaging we observed a spatial inhomogeneity in diastolic longitudinal strain rates in healthy persons. A base-to-apex time delay in diastolic lengthening could be seen both in early diastole and at atrial contraction. METHODS AND RESULTS: We investigated this consistent finding and its dependence on loading conditions in 20 healthy volunteers. Propagation velocities of lengthening of 91 +/- 31 cm/s (E-wave) and 203 +/- 11 cm/s (A-wave) at rest (equal to time delays of 104 +/- 29 ms and 56 +/- 24 ms, respectively) increased significantly to 101 +/- 27 cm/s (E) and 283 +/- 17 cm/s (A) with lifting the volunteers' legs. Applying nitroglycerin sublingually and sitting upright significantly decreased propagation velocities (E-wave 76 +/- 20 cm/s, A-wave 172 +/- 93 cm/s and E-wave 66 +/- 17 cm/s, A-wave 150 +/- 64 cm/s, respectively). Free lateral walls showed a lower propagation velocity than septal walls. CONCLUSION: We conclude that the propagation velocities of left ventricular lengthening waves are dependent on preload changes and increase with increasing preload.

Adult↗
PubMed2002

Can changes in systolic longitudinal deformation quantify regional myocardial function after an acute infarction? An ultrasonic strain rate and strain study.

OBJECTIVES: The aim of this study was to evaluate the additional value of ultrasonic strain rate and strain to myocardial velocity in the identification and quantification of regional asynergy after an acute myocardial infarction (MI). METHODS: Forty patients (59 +/- 13 years) were investigated 3 +/- 2 days after a first infarction and compared with 14 age-matched controls with normally contracting segments (group A, n = 146). Longitudinal myocardial velocities, strain rate (SR) and strain (epsilon) were postprocessed from basal, mid, and apical segments interrogated using apical views. In a subset of patients with coronary angiograms (n = 24), myocardial segments were divided into 3 groups: normally contracting segments supplied by a normal coronary artery (group B1), normally contracting segments supplied by a diseased coronary artery (group B2), and segments with abnormal motion (group B3). Velocities were decreased in patients with myocardial infarction (MI) (P <.05 vs controls) but failed to accurately differentiate normally from abnormally contracting segments. At the opposite end, systolic SR and epsilon decreased significantly with segmental asynergy severity and could identify infarct-involved segments (group B3) with a sensitivity/specificity of 85% (systolic SR and epsilon cutoff values of -0.8 s(-1) and -13%, respectively). CONCLUSION: Strain rate and strain can better assess segmental dysfunction severity than myocardial velocities alone after an acute MI.

Aged↗