Contraction Patterns In Patients Research Articles

Right ventricular mechanical pattern in patients undergoing mitral valve surgery: a predictor of post-operative dysfunction?

AimsThe PREPARE‐MVR study (PRediction of Early PostoperAtive Right vEntricular failure in Mitral Valve Replacement/Repair patients) sought to investigate the alterations of right ventricular (RV) contraction pattern in patients undergoing mitral valve replacement/repair (MVR) and to explore the associations between pre‐operative RV mechanics and early post‐operative RV dysfunction (RVD).Methods and resultsWe prospectively enrolled 42 patients (63 ± 11 years, 69% men) undergoing open‐heart MVR. Transthoracic three‐dimensional (3D) echocardiography was performed pre‐operatively, at intensive care unit discharge, and 6 months after surgery. The 3D model of the RV was reconstructed, and RV ejection fraction (RVEF) was calculated. We decomposed the motion of the ventricle to compute longitudinal ejection fraction (LEF) and radial ejection fraction (REF). Pulmonary artery catheterization was performed to monitor RV stroke work index (RVSWi). RVEF was slightly decreased after MVR [52 (50–55) vs. 51 (46–54)%; P = 0.001], whereas RV contraction pattern changed notably. Before MVR, the longitudinal shortening was the main contributor to global systolic RV function [LEF/RVEF vs. REF/RVEF; 0.53 (0.47–0.58) vs. 0.33 (0.22–0.42); P < 0.001]. Post‐operatively, the radial motion became dominant [0.33 (0.28–0.43) vs. 0.46 (0.37–0.51); P = 0.004]. However, this shift was temporary as 6 months later the two components contributed equally to global RV function [0.44 (0.38–0.50) vs. 0.41 (0.36–0.49); P = 0.775]. Pre‐operative LEF was an independent predictor of post‐operative RVD defined as RVSWi < 300 mmHg⋅mL/m2 [OR = 1.33 (95% CI: 1.08–1.77), P < 0.05].ConclusionsMVR induces a significant shift in the RV mechanical pattern. Advanced indices of RV mechanics are associated with invasively measured parameters of RV contractility and may predict post‐operative RVD.

Septal Flash-like Motion of the Earlier Activated Ventricular Wall Represents the Pathophysiology of Mechanical Dyssynchrony in Single-Ventricle Anatomy

In biventricular physiology, abnormal septal motion is a hallmark of mechanical dyssynchrony in the left bundle branch block. However, in single-ventricle (SV) physiology, morphologic variations in systemic ventricles pose a challenge in evaluating the negative impact of mechanical dyssynchrony. The present study aimed to characterize the pathologic dyssynchronous contraction patterns in patients with SV. In this retrospective study, 70 consecutive postoperative patients with SV anatomy with prolonged QRS duration (25 female patients; median age, 14years) were enrolled. We divided each SV into two regions and analyzed independent strains using two-dimensional speckle-tracking echocardiography. From an earlier activated ventricular wall, we calculated the strain ratio (Rstrains) of two values (%) during the QRS period and the ejection period: (100+Strainejection)/(100+StrainQRS). We reviewed the clinical profiles, B-type natriuretic peptide plasma levels, exercise capacity, and morbidity. Six patients who underwent cardiac resynchronization therapy (CRT) were analyzed regarding changes in strain patterns and ventricular volume. Higher Rstrains, indicating a preceding contraction and subsequent dyskinetic dilation of the earlier activated ventricular wall, was associated with increased B-type natriuretic peptide, reduced exercise capacity, and poor outcome. However, delayed contraction of the later activated ventricular wall was not associated with the effects. Decreases in Rstrains and ventricular volume reductions were observed in all patients afterCRT. A specific strain pattern in an earlier activated ventricular wall indicates mechanical dyssynchrony in patients with SV. This pattern is very similar to the septal flash in adult patients with left bundle branch block. This strategy might be a promising approach for selecting appropriate candidates for CRT in patients with SV.

5939Perioperative shift in right ventricular mechanical pattern in patients undergoing mitral valve surgery: a predictor of right ventricular failure?

Abstract Background Severe mitral regurgitation (MR) induces significant changes not only in the left, but also in the right ventricular (RV) morphology and function. Early treatment of MR is recommended, however, surgical procedure disrupts the native RV contractile pattern and predisposes the at-risk ventricle to develop postoperative RV failure (RVF) which is associated with poor outcomes. Purpose Accordingly, the PREPARE-MVR study (PRediction of Early PostoperAtive Right vEntricular failure in Mitral Valve Replacement/Repair patients) aims to explore the alterations of RV contraction pattern in patients undergoing MVR and to investigate the association of preoperative echocardiographic findings with early postoperative RVF. Methods We prospectively enrolled 70 patients (62±12 years, 67% males) undergoing open heart MVR. Thirty age and gender matched healthy volunteers served as control group. Transthoracic 3D echocardiography was performed preoperatively and at intensive care unit discharge. Furthermore, focused 2D echocardiogram was also obtained during the ICU stay. Forty-three patients also completed 6 months follow-up. 3D model of the RV was reconstructed and end-diastolic volume index (EDVi) along with RV ejection fraction (RVEF) were calculated. For in-depth analysis of RV mechanics, we decomposed the motion of the RV to compute longitudinal (LEF) and radial ejection fraction (REF). Right heart catheterization was performed to monitor RV stroke work index (RVSWi). Results RV morphology as assessed by EDVi was unaffected by surgery (preoperative vs postoperative; 73±17 vs 71±16 mL/m2, p=NS). RVEF was slightly decreased after MVR (52±6 vs 48±7%, p&lt;0.05), whereas RV contraction pattern has changed notably. Before MVR, the longitudinal shortening was the main contributor to global systolic function (LEF/RVEF vs REF/RVEF; 0.53±0.10 vs 0.43±0.12; p&lt;0.001), whereas in controls the longitudinal and radial shortening contributed equally to RVEF (0.47±0.07 vs 0.43±0.09; p=NS). Postoperatively, the radial motion became dominant (0.35±0.08 vs 0.47±0.09; p&lt;0.001). However, this shift was only temporary as 6 months later the contraction pattern became similar to controls showing equal contribution of the two components (0.44±0.10 vs 0.42±0.11; p=NS). Postoperative RVF (defined as RVSWi &lt;300 mmHg*mL/m2 or ICU TAPSE &lt;10 mm) was detected in 14 [20%] patients. Preoperative LEF was associated with postoperative RVSWi (r=−0.61, p&lt;0.001) and it was an independent predictor of postoperative RVF (OR=1.16 [1.03–1.35], p&lt;0.05). Conclusion Severe MR induces a significant shift in the RV mechanical pattern which may influence the development of postoperative RV dysfunction and failure after MVR. Advanced indices of RV mechanics are associated with invasively measured parameters of RV contractility and may predict postoperative RVF.

Radical prostatectomy restores detrusor contraction pattern according to pressure flow parameters.

Pressure flow studies are regarded as the gold standard for evaluating both bladder outlet obstruction and detrusor contractility, but none of the current methods for evaluating bladder contraction patterns are well validated. Impaired bladder contraction results in a lower peak Watts factor and poorly sustained detrusor contractions. From this viewpoint, the maximum Watts factor and its pattern should be considered separately. To examine detrusor contraction pattern in patients after radical prostatectomy by using multiple parameters. A total of 37 patients with clinically localized prostate cancer underwent both pre- and post-radical prostatectomy urodynamic evaluations. The examined urodynamic parameters included the maximum flow rate, post-void residual volume, detrusor pressure at maximum flow, maximum Watts factor and relative volume (maximum Watts factor). Some parameters were defined from the Watts factor curve throughout micturition. Relative volume (maximum Watts factor) was the relative bladder volume at the maximum Watts factor. A normal detrusor contractility pattern involves an increase in Watts factor at the initiation followed by further gradual increases until the end of micturition. Maximum flow rate increased significantly after radical prostatectomy (pre: 13.0±6.5, post: 17.3±7.7mL/min; P<0.01), whereas detrusor pressure at maximum flow and post-void residual volume decreased significantly (pre: 49.6±21.6 and 31.4±18.2cmH2 O; post: 48.6±66.1 and 10.1±28.5mL; P<0.05). Maximum Watts factor did not change significantly after radical prostatectomy (pre: 10.5±3.1W/m2 , post: 11.0±3.2W/m2 ), but relative volume (maximum Watts factor) decreased significantly (pre: 0.48±0.3, post: 0.20±0.20; P<0.001). Maximum Watts factor represents the maximum power of bladder contraction at a particular point in time, whereas relative volume (maximum Watts factor) can be used to detect changes in detrusor contraction pattern. Evaluation of relative volume (maximum Watts factor) confirms that radical prostatectomy restores the normal detrusor contractility pattern in prostate cancer patients.

Characteristic systolic waveform of left ventricular longitudinal strain rate in patients with hypertrophic cardiomyopathy.

We analyzed the waveform of systolic strain and strain-rate curves to find a characteristic left ventricular (LV) myocardial contraction pattern in patients with hypertrophic cardiomyopathy (HCM), and evaluated the utility of these parameters for the differentiation of HCM and LV hypertrophy secondary to hypertension (HT). From global strain and strain-rate curves in the longitudinal and circumferential directions, the time from mitral valve closure to the peak strains (T-LS and T-CS, respectively) and the peak systolic strain rates (T-LSSR and T-CSSR, respectively) were measured in 34 patients with HCM, 30 patients with HT, and 25 control subjects. The systolic strain-rate waveform was classified into 3 patterns ("V", "W", and "√" pattern). In the HCM group, T-LS was prolonged, but T-LSSR was shortened; consequently, T-LSSR/T-LS ratio was distinctly lower than in the HT and control groups. The "√" pattern of longitudinal strain-rate waveform was more frequently seen in the HCM group (74%) than in the control (4%) and HT (20%) groups. Similar but less distinct results were obtained in the circumferential direction. To differentiate HCM from HT, the sensitivity and specificity of the T-LSSR/T-LS ratio <0.34 and the "√"-shaped longitudinal strain-rate waveform were 85 and 63%, and 74 and 80%, respectively. In conclusion, in patients with HCM, a reduced T-LSSR/T-LS ratio and a characteristic "√"-shaped waveform of LV systolic strain rate was seen, especially in the longitudinal direction. The timing and waveform analyses of systolic strain rate may be useful to distinguish between HCM and HT.

A U-shaped type II contraction pattern in patients with strict left bundle branch block predicts super-response to cardiac resynchronization therapy.

New criteria to define strict left bundle branch block (LBBB) on the basis of pathophysiological principles predict response to cardiac resynchronization therapy (CRT). Heterogeneous activation and contraction patterns have been identified in patients with classical LBBB. Cardiac magnetic resonance (CMR) imaging has demonstrated that a U-shaped (type II) contraction predicts reverse remodeling post-CRT. A homogeneous spread of (type I) contraction is less predictive. The purpose of this study was to investigate contraction patterns among patients with strict LBBB and to test whether a type II contraction pattern better predicts CRT response and super-response. Thirty-seven patients with strict LBBB (QRS duration ≥140 ms for men and ≥130 ms for women with mid-QRS notching or slurring in ≥2 contiguous leads) underwent cine CMR imaging pre-CRT with an analysis of their contraction patterns by using endocardial contour tracking software. Patients were evaluated for reverse remodeling 6 months postimplantation. Nineteen patients (51%) had a type II contraction pattern. A total of 25 patients (68%) of the cohort reverse remodeled. In the type II contraction group, all 19 patients (100%) reverse remodeled as compared with 6 patients (33%) in the type I contraction group (P < .01). Super-response was achieved in 21 patients (57%) of the total cohort: 5 patients with a type I contraction pattern (28%) and 16 patients with a type II contraction pattern (84%) (P < .01). Patients with strict LBBB who are guideline indicated for CRT have heterogeneous contraction patterns derived from cine CMR. A type II contraction pattern is strongly predictive for reverse remodeling and super-response. This questions whether strict LBBB criteria alone are sufficient to reliably predict a positive response to CRT.

Left ventricular contraction pattern in asymptomatic patients with moderate to severe aortic regurgitation

Background: The aim of the study was to compare systolic left ventricular (LV) contraction pattern in patients with moderate to severe aortic regurgitation (AR) with healthy controls (C) by real-time three-dimensional echocardiography (RT3DE). Methods: Twenty patients and 15 age matched controls were compared (35±4 (SD) and 38±9 years, respectively, p=NS). All were examined with transthoracic three-dimensional speckle tracking. LV end-diastolic volume LVEDV, end-systolic volume (LVESV), LV ejection fraction (LVEF), LV mass index (LVMi) and global tissue deformation parameters (strain and strain rate) were measured in the three orthogonal axes (long axis, circumferential axis and radial axis). Results: Heart rate was similar in the AR and the C group (62±11 and 59±8 bpm, respectively, p=NS). Brachial pulse pressure was higher in AR patients (71±17 vs 50±5 mmHg, p< 0,02). In the two groups (AR vs C) LVEDV was (233±37 and 145±23 ml (p<0,02), LVESV 87±15 and 58±10 ml (NS), LVEF (63±3 and 61±2%) (p=NS) and LVMi (119±23 and 87±11 g/m2 (p<0,02). Peak global systolic longitudinal strain and strain rates were reduced in the AR group (-0,16±0,02 vs 0,18±0,02, p<0,02) and (-0,73±0,10 vs -0,83±0,08 1/s, p<0,02), while peak systolic circumferential and radial strains (-0,18±0,03 vs -0,17±0,02, p=NS and 0,47±0,07 vs 0,49±0,05, p=NS) and strain rates (-0,84±0,10 vs -0,84±0,10 1/s) did not differ between groups (p=NS). Systolic longitudinal strain and strain rates correlated well with EDV (p=0,004 and p=0,021, respectively), while no correlation was demonstrated for circumferential or radial strain/strain rate (p=NS). Conclusion: RT3DE identifies non-homogenous remodeling in patients with chronic moderate to severe aortic regurgitation. Isolated reduction of longitudinal strain and strain rate was demonstrated, and was strongly correlated to the volume loaded left ventricle.

Circumferential myocardial contraction patterns in patients with idiopathic frequent premature ventricular complexes from the right ventricular outflow tract

BackgroundThe pathogenesis of frequent premature ventricular complexes (PVCs) in patients without overt cardiovascular disease is considered idiopathic. Idiopathic PVCs are predominantly from the right ventricular outflow tract (RVOT) and considered a reversible cause of left ventricular (LV) dysfunction. ObjectivesWe investigated whether alternations in LV contraction patterns exist in patients with idiopathic frequent PVCs originating from the RVOT. MethodsSegmental myocardial circumferential strain (CS)–time curves were acquired from 29 patients with idiopathic frequent RVOT-PVCs and 30 healthy subjects. Peak CS and the time to peak CS (TPcs) of each segment were analyzed, with the standard deviation of TPcs for 18 LV segments (SDtpcs) calculated. All values of patients with RVOT-PVCs were recorded during both sinus beats (PVC-S) and ventricular extrasystoles (PVC-V), respectively. ResultsThe distribution of peak CS and TPcs in the PVC-V was opposite that of the healthy subjects. The distribution of TPcs of PVC-S within the different layers differed from that of healthy subjects. These patients had significantly greater dyssynchrony compared with the healthy subjects assessed by SDtpcs (healthy subjects: 6.7%±1.9%, PVC-S: 8.1%±3.1%, PVC-V: 9.7%±3.4%, healthy subjects vs. PVC-S p=0.04; healthy subjects vs. PVC-V p=0.001). Furthermore, a positive correlation was observed between PVC frequency and SDtpcs of PVC-S (r=0.44, p=0.02). ConclusionsIdiopathic frequent RVOT-PVCs can induce alterations in the LV myocardial contractile pattern during both sinus beats and ventricular extrasystoles. Circumferential contraction dyssynchrony of patients during sinus beats relates to PVC frequency. Therefore, attention should be paid to patients with frequent RVOT-PVCs, especially those with a high prevalence of PVCs.

Left Ventricular Contraction Patterns in Patients With Suspected Acute Coronary Syndrome and Normal Coronary Angiograms: A New Look at the Takotsubo Syndrome

Original descriptions of the takotsubo syndrome (TS) included a characteristic left ventricular (LV) contraction pattern, "apical ballooning." Recently, several reports have associated contraction patterns not strictly conforming to the original description with TS. The specifics of the contraction pattern seem to set TS apart from the much larger population of patients with acute coronary syndrome (ACS) but no obstructive coronary artery disease (OCAD). This study was undertaken to compare patients with midventricular and apical dysfunction with those with other LV contraction patterns. If TS can present with a variety of patterns of LV dysfunction, then both those with and those without the pattern should have the clinical components previously assigned to the syndrome. We studied LV contraction patterns in consecutive ACS patients referred for consideration of emergent or urgent percutaneous coronary intervention. Of the 893 patients evaluated in 2008, we excluded 862 on the basis of OCAD, preexisting LV dysfunction, or an obvious alternative cause of symptoms. The remaining 31 (3.5%) also had no OCAD but manifested an LV contraction abnormality. We compared the 15 patients (1.7%) whose ventriculograms met criteria for TS with the 16 patients (1.8%) whose did not. The most common alternative pattern was global hypokinesis, followed by a variety of segmental contraction abnormalities. Patients with the TS pattern were older and had evidence of greater myocardial injury. More than 85% were women. The TS pattern identifies a distinct subset of ACS patients with a remarkable predominance of postmenopausal women and is therefore fundamental to the definition of this entity. This distinctive facet of the syndrome is likely to be an important clue to its pathogenesis. We did not encounter patients with other patterns of LV dysfunction that could be thought to represent stress-induced cardiomyopathy. Copyright © 2011 Wiley Periodicals, Inc. The authors have no funding, financial relationships, or conflicts of interest to disclose.

Atrial Electromechanical Sequence and Contraction Synchrony during Single‐ and Multisite Atrial Pacing in Patients with Brady‐Tachycardia Syndrome

Investigation of which atrial pacing modality provides atrial synchrony and the most physiological atrial contraction pattern in patients with brady-tachycardia syndrome. Fifteen healthy subjects and 57 patients with sinus node dysfunction, atrial fibrillation recurrences, and prolonged P-wave on the electrocardiogram treated with multisite atrial (MSA) pacing were studied. One atrial lead was implanted in the coronary sinus (CS) ostium area, the other at the right atrial appendage (RAA): RAA+CS group (28 patients), or Bachmann's bundle (BB) region: BB+CS group (29). Sinus rhythm (SR) and CS, RAA, BB, RAA+CS, and BB+CS pacing modalities were evaluated. Electromechanical delay (EMD) in atrial walls was assessed by tissue Doppler echocardiography. Interatrial (DeltainterA), intra-right (DeltaRA), and intra-left (DeltaLA) atrial dyssynchrony were calculated. During SR, in the study group versus controls, important DeltainterA: 55 +/- 23 versus 22 +/- 11 ms (P < 0.01) and DeltaLA: 47 +/- 21 versus 21 +/- 6 ms (P < 0.001) were present. Single-site BB and both MSA pacing modes restored DeltainterA and DeltaLA (DeltainterA: 24 +/- 16, 20 +/- 13 and 14 +/- 9 ms, DeltaLA: 28 +/- 18, 28 +/- 13 and 20 +/- 10 ms during BB, RAA+CS and BB+CS pacing, respectively). CS pacing prolonged lateral RA EMD, while RAA pacing LA walls EMD, which resulted in DeltainterA persistence. CS pacing induced DeltaRA (50 +/- 23 vs 16 +/- 8 ms, P < 0.0001 vs controls). Atrial contraction sequence during BB pacing resembled that observed in controls. (1) Single-site BB and both MSA pacing modes restored atrial synchrony. (2) Single-site RAA and CS ostium pacing retained interatrial dyssynchrony; moreover, CS pacing created RA dyssynchrony. (3) Single-site BB pacing provided physiological atrial contraction sequence.

Cardiac Resynchronization Improves Coronary Blood Flow

Asynchronous ventricular activation, induced by left bundle branch block, is known to have deleterious effects on the systolic and diastolic functions of the left ventricle (LV). Cardiac resynchronization therapy (CRT) has been proposed as a complementary method to improve the LV systolic performance by restoring the synchronized contraction patterns in patients with advanced heart failure and left bundle branch block. However, the effect of CRT on myocardial blood flow is not well established. In the present study, we therefore examined the coronary blood flow in 20 patients with idiopathic dilated cardiomyopathy, implanted with a biventricular pacemaker according to the established CRT criteria. Color Doppler settings were adjusted for the optimal coronary flow imaging, and coronary flow velocities were obtained in all patients. Typical diastolic predominant phasic Doppler spectrum of the distal left anterior descending coronary artery (LAD) was recorded. Conventional echocardiographic variables, peak values of the diastolic and systolic LAD velocities, and the velocity time integrals were measured for three or five consecutive beats during CRT with pacemaker on and off. Successful CRT with biventricular pacing increased coronary blood flow velocities of the distal LAD in addition to its well-known benefits on the systolic and diastolic LV performance in patients with significant dyssynchrony. CRT decreased duration of mitral regurgitation and increased diastolic filling time. Peak diastolic velocities and velocity time integral of the distal LAD were increased significantly. In conclusion, successful CRT with biventricular pacing improves coronary blood flow velocities of the distal LAD.

A07-2 Influence of LBBB, RBBB, DDD and BIV pacing on ventricular contraction pattern in patients with dilative cardiomyopathy

A07-2 Influence of LBBB, RBBB, DDD and BIV pacing on ventricular contraction pattern in patients with dilative cardiomyopathy

A07-2 Influence of LBBB, RBBB, DDD and BIV pacing on ventricular contraction pattern in patients with dilative cardiomyopathy

A07-2 Influence of LBBB, RBBB, DDD and BIV pacing on ventricular contraction pattern in patients with dilative cardiomyopathy

Unique contraction pattern in patients after coronary bypass graft surgery by gated SPECT myocardial perfusion imaging.

Although left ventricular systolic function seems to be accurately represented on gated SPECT myocardial perfusion imaging, specific patterns of wall motion (WM) and thickening after coronary bypass graft surgery (CABG), demonstrated by other imaging methods, have not been characterized for gated SPECT myocardial perfusion imaging. Gated SPECT myocardial perfusion imaging was studied in 30 consecutive patients after CABG (group 1) and 40 non-CABG patients-30 with normal stress perfusion studies (group 2) and 10 with known previous anterior wall infarction (group 3). Two expert readers evaluated epicardial and endocardial systolic WM. Regional WM and the thickening percentage were obtained using CEQUAL 20 segment bull's eye analysis and compiled into regional values. Qualitatively, the post-CABG patients had hypokinetic septum, a hyperdynamic lateral wall, and preservation of anterior WM. In 25 of 30 (83.3%) patients, an anterior systolic epicardial "swing" was evident and was different from the inward endocardial and epicardial motion seen in groups 2 and 3. Septal WM was decreased in group 1 compared with group 2 (2.9 vs. 6.0 mm, < 0.001), with no significant difference in septal thickening. This was not different from the reduced septal motion seen in group 3 (4.1 mm), which was accompanied by both reduced thickening and abnormalities of anterior WM. Lateral WM was increased in group 1 compared with group 2 (9.9 vs. 8.2, < 0.001), with no significant difference in lateral wall thickening (34.6% vs. 39%). There is a characteristic contraction pattern on gated SPECT myocardial perfusion imaging in post-CABG patients distinguished by apparent septal hypokinesis with preservation of septal wall thickening, apparent increase in endocardial lateral WM, and an anterior epicardial "swing," different from the contraction pattern seen in normal patients and those with previous anterior wall infarction. The related perfusion pattern aids in evaluation of the mechanism of these findings.

Non-parametric Classification of Esophagus Motility by Means of Neural Networks

Automatic long-term recording of esophageal pressures by means of intraluminal transducers is used increasingly for evaluation of esophageal function. Most automatic analysis techniques are based on detection of derived parameters from the time series by means of arbitrary rule-based criterions. The aim of the present work has been to test the ability of neural networks to identify abnormal contraction patterns in patients with non-obstructive dysphagia (NOBD). Nineteen volunteers and 22 patients with NOBD underwent simultaneous recordings of four pressures in the esophagus for at least 23 hours. Data from 21 subjects were selected for training. The performances of two trained networks were subsequently verified on reference data from 20 subjects. The results show that non-parametric classification by means of neural networks has good potentials. Back propagation shows good performance with a sensitivity of 1.0 and a specificity of 0.8.

Electrophysiological Remodeling of the Heart Owing to Rate

Although damage to the heart from inflammation and infarction are well-established stimuli that trigger major cardiac remodeling, it has been known since 1954 that a persistent supraventricular tachycardia also can alter cardiac structure and function.1 This clinical observation was exploited 8 years later when it was demonstrated that rapid stimulation of the normal heart could produce reversible congestive heart failure.2 Since then, rapid pacing has been used frequently to create an investigational animal model of heart failure. The effects of prolonged pacing-induced tachycardia, in the range of 250 bpm for 3 or 4 weeks, has been studied in depth in several animal species and has been shown to cause extensive myocardial remodeling. Biventricular enlargement with reduced wall thickness and no increase in muscle mass, reduced cross-sectional myocyte area and increased length, disarray of myofibril alignment and cytoarchitecture, increases in contractile protein degradation, and destruction of the supporting myocardial collagen matrix represent some of the structural changes contributing to reduced ventricular function.3 Diminished responsiveness to β-adrenoceptor stimulation caused by a reduction in β-receptor density and a variety of alterations in the adrenergic signaling processes also occur.4 Replacement fibrosis, loss of cells, and reactive hypertrophy of the remaining cells have been noted recently.5 mRNA levels for specific cytoskeletal proteins increase, along with alterations in cytoskeletal architecture6 and abnormalities in phospholamban.7 In pigs subjected to 3 weeks of a tachycardia-induced cardiomyopathy, myocyte action potential showed reduced membrane resting potential, reduced amplitude and upstroke velocity, and prolonged duration at 90% repolarization. Peak L-type Ca2+ current density was reduced because of an absolute reduction in L-type Ca2+ current flow into the myocyte possibly caused by reduced open probability of the channel.8 However, in dogs that had rapid ventricular pacing for 3 to 4 weeks, action …

Abnormal ventricular contraction patterns in patients with arrhythmogenic substrates using three-dimensional phase analysis.

Arrhythmogenic substrate diagnosis has been achieved by electrophysiological studies and best localized by successful radiofrequency ablation. Pre-invasive localization procedures have been based on surface ECGs and more recently on biomagnetism, but in addition to these electric and magnetic signals a mechanical signal may be utilized: the initial site of contraction may be detected by phase analysis during radionuclide ventriculography. Generation of three-dimensional data set of phases is achieved by incorporating the new emission tomography technique. The performance of this modified phase analysis has been investigated for the detection of the normal contraction pattern during sinus rhythm, the arrhythmogenic substrate of the WPW syndrome and ventricular tachycardia, and further, to define the limitations of the method in experimental studies on pigs. In 30 out of 44 patients with normal sinus rhythm and no ventricular lesion, a characteristic phase pattern was found. Physiologically, the initial site of contraction appeared to be paraseptal and in the anterior wall of the right ventricle close to the apex. In 13 patients with WPW syndrome and in seven with ventricular tachycardia, the phase data were compared to the electrophysiological study. In 14 of 20 there was a complete match, in 3 of 20 a mechanical focus was found in the area adjacent to the electric focus. From experimental pig studies with simulated stimulation, a spatial precision of at least 20 mm was found at a pre-excitation of 20 ms.(ABSTRACT TRUNCATED AT 250 WORDS)

Uterine Contraction Patterns in Patients with Severe Abruptio Placentae

Department of Obstetrics and Gynecology, University of Stellenbosch and Tygerberg Hospital, Parovallei, CP S.

Mechanical and electromyographic aspects of contraction patterns in patients with peripheral nerve complaints

Mechanical and electromyographic aspects of contraction patterns in patients with peripheral nerve complaints