Left ventricular mechanics in dilated cardiomyopathy

The influence of altered chamber shape on the evaluation of left ventricular (LV) mechanics in idiopathic dilated cardiomyopathy (IDC) is unknown. Nine patients with IDC and 7 subjects with normal LV function were studied with simultaneous LV pressure and M-mode echographic recordings in order to derive LV meridional wall stress. The major axis of the left ventricle, determined from the left ventriculogram at rest, allowed for derivation of circumferential wall stress. The IDC group was characterized by larger end-diastolic and end-systolic LV volumes, increased LV mass, depressed angiographic ejection fraction and more spherical LV chamber shape. Both end-systolic meridional (114 +/- 30 kdyne/cm2) and circumferential (251 +/- 73 kdyne/cm2) wall stresses were elevated in patients with IDC, although the ratio of these stresses was less than normal (2.2 +/- 0.1 vs 2.7 +/- 0.2, respectively). LV load alteration with phenylephrine or nitroglycerin allowed for construction of end-systolic stress-minor-axis dimension and end-systolic stress-minor-axis shortening relations. Similar mean slopes of the meridional end-systolic stress-dimension relation were noted in IDC and normal subjects, although the line was displaced to the right in IDC. The slope of the circumferential end-systolic stress-dimension relation was, however, decreased in patients with IDC. Moreover, the end-systolic stress-fractional minor-axis shortening relation in patients with IDC was displaced downward from the normal relation supporting depressed contractile function in these IDC patients.(ABSTRACT TRUNCATED AT 250 WORDS)     

Left ventricular torsional mechanics in uncomplicated pregnancy

Background:

Alterations in left ventricular (LV) twist (torsion) and untwist have been described for a variety of physiologic and pathologic conditions. Little information is available regarding changes in these parameters during normal pregnancy.

Hypothesis:

Pregnancy is associated with significant changes in LV torsional mechanics.

Methods:

Left ventricular twist and untwist was measured in 32 pregnant females (mean gestation 199 ± 48 d) and 23 nonpregnant controls using speckle‐tracking echocardiography.

Results:

Left ventricular ejection fraction (68 ± 5% vs 66 ± 5%) was similar between the groups (P not significant). There was a significant increase in peak LV twist from nonpregnant controls (9.4 ± 3.7 degrees) to second‐trimester (12.0 ± 4.2 degrees) and third‐trimester subjects (12.6 ± 5.9 degrees, all P<0.05). Peak LV twist velocity was also increased in second‐ and third‐trimester groups compared with controls (94 ± 24 degrees/sec and 93 ± 30 vs 64 ± 21 degrees/sec, respectively, both P<0.05). Both peak untwist velocity and time to peak untwist velocity were not significantly different between groups (P not significant). Multiple regression analysis indicate that only systolic blood pressure (r = 0.394, P = 0.005) was an independent predictor for increased LV torsion.

Conclusions:

There are significant changes in LV torsional indices during the course of pregnancy, whereas untwist parameters remain unchanged. Blood pressure is independently associated with increased torsion during pregnancy. © 2011 Wiley Periodicals, Inc. The authors have no funding, financial relationships, or conflicts of interest to disclose.     

Left ventricular function in normal newborn infants and asymptomatic infants with neonatal polycythemia

Digitized M-mode echocardiography was used to evaluate left ventricular (LV) function in normal neonates and to document subtle abnormalities of LV function in 19 asymptomatic newborn infants with polycythemia and hyperviscosity. Echocardiograms were performed before and after partial exchange transfusion and at 48 hours of age. Results were compared to those obtained from analysis of echocardiograms from 18 normal infants with normal hematocrits at 12 and 48 hours of age. In the normal group there were no differences between the digitized indices of LV function at 12 hours and those at 48 hours of age. In the polycythemic group, prior to hemodilution, the peak rate of LV emptying was low compared to normal values (-3.1 +/- 0.7 sec-1 vs -3.6 +/- 1.0 sec-1, p less than 0.05) and normalized following the procedure to -3.7 +/- 1.3 sec-1. The peak rate of left ventricular posterior wall (LVPW) thickening also increased following partial exchange transfusion (3.2 +/- 0.6 sec-1 to 3.7 +/- 1.0 sec-1, p less than 0.05). At 48 hours of age peak rates of change for the left ventricle (-2.9 +/- 0.8) and LVPW (3.0 +/- 0.7) were abnormally low in the polycythemic infants, all of whom had undergone partial exchange transfusion. Also, at 48 hours, the LVPW time to peak rate of thickening and time to the end of thickening were prolonged. In addition, the peak rate of LV filling in diastole was low in the polycythemic group (3.0 +/- 0.9 sec-1 vs 3.9 +/- 1.3 sec-1, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Left ventricular midwall mechanics in subjects with aortic stenosis and normal systolic chamber function

BACKGROUND AND AIM OF THE STUDY: Endocardial indices of left ventricular (LV) systolic function overestimate myocardial performance in hypertrophic left ventricles. Midwall fractional shortening (mFS) is a more reliable index of systolic performance. Aortic stenosis (AS) is a common cause of LV hypertrophy (LVH), but midwall mechanics in this condition have not been analyzed. Also, a tendency towards hyperdynamic LV chamber function has been reported in women with AS in comparison with men, but whether there exist gender-related discrepancies in midwall performance is not known. METHODS: The study group included 147 patients with AS and normal chamber systolic function. LV diameters and thicknesses, LV mass, relative wall thickness (RWT), endocardial fractional shortening, stroke volume, ejection fraction (EF), mFS and stress-corrected mFS were determined. RESULTS: Patients with AS showed depressed mFS (16.2 +/- 2.5% versus 18.8 +/- 2.4%, p <0.0001) and stress-corrected mFS (84.3 +/- 13.8% versus 100.0 +/- 12.6%, p <0.0001) when compared to controls. The subset with moderate AS had lower mFS (15.9 +/- 2.0%) than those with mild AS (16.9 +/- 2.4%), and further depression was present in subjects with severe AS (13.8 +/- 2.2%, p <0.0001). A similar trend was observed for stress-corrected mFS (mild AS, 88.5 +/- 13.3%; moderate AS, 82.0 +/- 11.5%; severe AS, 71.2 +/- 12.0%, p <0.0001). Multivariate analysis identified RWT as the best predictor of mFS and stress-corrected mFS. Logistic regression showed that depressed stress-corrected mFS was independently associated with the presence of symptoms. Endocardial fractional shortening and EF were increased in women compared to men, but there were no gender-related differences in mFS (16.2 +/- 2.5% versus 16.1 +/- 2.4%, p = 0.84) and stress-corrected mFS (84.0 +/- 14.1% versus 84.5 +/- 13.5%, p 0.82). CONCLUSION: Aortic stenosis is associated with depression in LV midwall mechanics. Systolic midwall performance reduces as the severity of valve disease increases, and this relationship is mediated by parallel changes in LV geometry.     

Left ventricular diverticulum repair in a newborn

We report on a male newborn requiring repair of a huge left apical diverticulum leading to progressive heart failure and extensive ventricular arrhythmia. At the age of 11 days, a modified Dor procedure using an autologous endoventricular pericardial patch was performed. Postoperatively, a significant reduction of ventricular extrasystole was evident. One year postoperatively, the infant demonstrates a normal cognitive and somatic development without clinical signs of cardiac failure.     

Left ventricular dimensions and mechanics in distance runners

We assessed heart size and mechanics at rest in highly trained distance runners. By means of two-dimensional echocardiography, we compared 62 runners (greater than 40 miles/week) and 84 nonrunners. Left ventricular end-diastolic volume index and mass index were larger in runners than in nonrunners (p less than 0.001) and in men than in women (p less than 0.001). However, left ventricular end-diastolic and end-systolic volume/mass ratios were similar for runners and nonrunners. Noninvasive estimates of end-systolic and peak-systolic meridional and circumferential wall stresses were lower in runners than in nonrunners (p less than 0.001). Lower wall stress resulted from lower myocardial area/cavity area ratios, and thus 'average' radius/thickness ratios (measured from the parasternal short-axis view), in runners than in nonrunners (p less than 0.001). We detected a subtle change in ventricular shape among the distance runners. Basilar hypertrophy accounted for increased myocardial thickness with normal cavity size in the parasternal short-axis view, as might be expected in hearts working under sustained pressure elevations during prolonged training periods. However, cavity length and therefore ventricular volume were increased in the apical views, leading to a normal overall volume/mass ratio. These hearts have thus adjusted to periods of volume, as well as to pressure overload. Race performance is determined by a complex interaction between the heart, vascular, and skeletal muscle systems. In this study no parameter of myocardial size or function predicted 10 km or marathon race times, just as no physical characteristic or training record predicted left ventricular mass, end-diastolic or end-systolic volume.(ABSTRACT TRUNCATED AT 250 WORDS)     

Left ventricular thrombi in the presence of normal left ventricular function

We report two cases of left ventricular thrombi identified by routine echocardiography in the presence of normal ventricular function to highlight the rarity and clinical significance of this condition. A 14-year-old boy, positive for anticardiolipin and antinuclear antibodies, was found to have a left ventricular thrombus. A 30-year-old male, who presented with a transient ischemic attack, was found to have hypereosinophilic syndrome and a mobile left ventricular thrombus. The thrombi disappeared in both patients after a few days of anticoagulant therapy without symptoms of embolization.     

Left ventricular muscle and fluid mechanics in acute myocardial infarction

Left ventricular (LV) diastolic filling is characterized by the formation of intraventricular rotational bodies of fluid (termed "vortex rings") that optimize the efficiency of LV ejection. The aim of the present study was to evaluate the morphology and dynamics of LV diastolic vortex ring formation early after acute myocardial infarction (AMI), in relation to LV diastolic function and infarct size. A total of 94 patients with a first ST-segment elevation AMI (59 ± 11 years; 78% men) were included. All patients underwent primary percutaneous coronary intervention. After 48 hours, the following examinations were performed: 2-dimensional echocardiography with speckle-tracking analysis to assess the LV systolic and diastolic function, the vortex formation time (VFT, a dimensionless index for characterizing vortex formation), and the LV untwisting rate; contrast echocardiography to assess LV vortex morphology; and myocardial contrast echocardiography to identify the infarct size. Patients with a large infarct size (≥ 3 LV segments) had a significantly lower VFT (p <0.001) and vortex sphericity index (p <0.001). On univariate analysis, several variables were significantly related to the VFT, including anterior AMI, LV end-systolic volume, LV ejection fraction, grade of diastolic dysfunction, LV untwisting rate, and infarct size. On multivariate analysis, the LV untwisting rate (β = -0.43, p <0.001) and infarct size (β = -0.33, p = 0.005) were independently associated with VFT. In conclusion, early in AMI, both the LV infarct size and the mechanical sequence of diastolic restoration play key roles in modulating the morphology and dynamics of early diastolic vortex ring formation.     

Left ventricular mass in normal Indian population.

A prospective study was conducted to ascertain the distribution of the left ventricular mass in normal adult Indian population and to establish the upper limit of the same. Four hundred and eighty normal subjects (men = 310; women = 170), in the age group of 18 to 60 years were screened echocardiographically, to estimate the left ventricular mass. The left ventricular mass in men was found to be 124 +/- 32 gm whereas in women it was 93 +/- 37 gm. The upper limit of the left ventricular mass (mean +/- 2 SD) was found to be 189 gm and 167 gm, for men and women respectively. The left ventricular mass in both men and women correlated with the body weight (r = 0.51, p less than 0.001; r = 0.22, p less than 0.001), height (r = 0.27, p less than 0.001; r = 0.22, p less than 0.01), and the body surface area (r = 0.49, p less than 0.001; r = 0.27, p less than 0.001), whereas it was found to be independent of age (r = 0.01, p = NS; r = 0.10, p = NS). In men alone the diastolic blood pressure influenced the left ventricular mass (r = 0.27, p less than 0.001), otherwise the left ventricular mass was independent of systemic blood pressure variations within the normal range. The left ventricular mass in the present study differs significantly from the Western population.     

Left ventricular mechanics and myocardial blood flow following restoration of normal activation sequence in paced patients with long-term right ventricular apical stimulation

STUDY OBJECTIVES: Asynchronous ventricular activation, as induced by ventricular pacing, is known to affect left ventricular (LV) systolic and diastolic function and myocardial blood flow. However, it is not clear whether the long-term disturbances it causes are reversible after the restoration of the normal ventricular activation sequence. DESIGN: In this study, we used the conductance catheter method and a Doppler guidewire to assess the changes in LV mechanics, and correspondingly in myocardial blood flow, after the restoration of the normal ventricular activation sequence in patients with long-term right ventricular apical pacing. PATIENTS: Sixteen patients (mean [+/- SD] age, 61 +/- 11 years; 9 men) with right ventricular apical stimulation and complete ventricular pacing capture for a very long period were studied. In eight patients, we analyzed pressure-volume loops before and immediately after the restoration of the normal ventricular activation sequence, and in the remaining eight patients the myocardial blood flow and flow reserve were analyzed. Measurements and results: End-systolic elastance (Ees) [5.503 +/- 0.6 vs 4.287 +/- 0.28 mm Hg/mL, respectively; p = 0.003] and its ratio to effective arterial elastance (1.63 +/- 0.51 vs 2.00 +/- 0.64, respectively; p = 0.009), which are indexes of systolic function and ventriculoarterial coupling, respectively, improved significantly after restoration of the normal ventricular activation sequence. Indexes of diastolic function and the predicted myocardial oxygen consumption (MO(2)) showed no clear change. Coronary flow in the dominant coronary artery increased significantly (46.55 +/- 14.12 vs 71.55 +/- 27.53 mL/min, respectively; p = 0.002), while the coronary flow reserve in the same artery decreased (3.5 +/- 1.0 vs 2.6 +/- 0.5, respectively; p = 0.008). CONCLUSIONS: The restoration of a normal activation sequence after long-term ventricular asynchrony enhances acutely contractile function without affecting MO(2). These changes in LV function do not appear to have causal relationships with myocardial blood flow changes.     

Left ventricular chamber and wall mechanics in the presence of concentric geometry.

BACKGROUND: To test the hypothesis that in the presence of left ventricular concentric geometry the definition of 'normal' ejection fraction should be reconsidered, and normality should rather be considered to have a higher than usual lower limit METHODS: M-mode echocardiographic endocardial shortening (eS) was studied in 148 hypertensive patients with left ventricular concentric geometry (relative wall thickness > or = 0.42), 78 with normal (54 +/- 10 years, 27 women) and 70 with depressed midwall shortening (mS) (53 +/- 10 years, 26 women), based on normal distribution of stress-corrected mS, and compared to a reference adult population of 297 age-matched normal subjects (54 +/- 8 years, 121 women) with eS > or = 28%. RESULTS: Patients with low mS exhibited higher heart rates and body mass indices than control individuals (both P < 0.01); blood pressure, left ventricular mass, relative wall thickness and peripheral resistance were higher than in patients with normal mS, whereas cardiac index was reduced (all P< 0.01). Adjustment for body mass index and race attenuated but did not eliminate the differences between the two groups of patients (0.05 < P < 0.0001). In contrast, eS was higher than normal in patients with normal midwall shortening, whereas was 'normal' in patients with low left ventricular midwall function. More than 80% of patients in the lowest quartile of apparently normal eS exhibited clear-cut low left ventricular midwall function. CONCLUSIONS: 'Normal' left ventricular chamber function in the presence of concentric geometry is associated with depressed midwall performance, more severe left ventricular hypertrophy, lower cardiac output and higher peripheral resistance. 'Normal' eS is the hallmark of normal myocardial function when left ventricular geometry is normal, but should be considered as a marker of systolic dysfunction when associated with concentric left ventricular geometry. Normal limits for eS should be therefore reset to upper values.     

Left ventricular geometry and survival in patients with normal left ventricular ejection fraction

In hypertensive populations, left ventricular (LV) geometry, which is characterized by hypertrophy, predicts cardiovascular outcome. The left ventricle can also alter its shape by concentric remodeling (CR) in the absence of LV hypertrophy, a feature that is detected by echocardiography. This study assessed the prevalence and prognostic significance of various forms of LV geometry and changes in LV geometry over time in patients with normal LV systolic function. Retrospective analysis of a large clinical population (n = 35,602) that was referred for echocardiography was done, with all-cause mortality as the primary outcome. Abnormal LV geometry was identified in 46% of patients, with CR present in 35% (n = 12,362) and LV hypertrophy in 11% (n = 3,958). Patients with abnormal LV geometry were older and more obese compared with subjects with normal LV geometry. There was a strong relation between abnormal LV geometry and mortality, and patients with CR and LV hypertrophy exhibited considerably higher relative risk for all-cause mortality compared with subjects with normal LV geometry (relative risk [RR] 1.99, 95% confidence interval [CI] 1.88 to 2.18, p <0.0001; RR 2.13, 95% CI 1.89 to 2.40, p <0.0001, respectively). Subjects with CR who reverted to a normal geometric pattern had improved survival (RR 0.64, 95% CI 0.42 to 0.97, p = 0.03) compared with those who progressed to LV hypertrophy (RR 1.54, 95% CI 1.01 to 2.47, p = 0.05). In conclusion, CR, a form of cardiac adaptation, is frequently noted in patients with normal LV ejection fractions and confers a risk of death similar to that of LV hypertrophy. Normalization of CR is associated with better survival, whereas transition to LV hypertrophy increases mortality.     

Left ventricular remodeling and mechanics after successful repair of aortic coarctation

Forty normotensive patients (mean age 12.3 +/- 6.5 years) followed up after a successful repair of aortic coarctation (mean age at coarctectomy 5.1 +/- 4.8 yrs) were studied by echo-Doppler to (1) evaluate left ventricular (LV) remodeling and endocardial and midwall mechanics, and (2) identify factors that might predispose to persistent abnormalities. Sex- and age-specific cutoff levels for LV mass/height2.7 and relative wall thickness were defined to assess LV geometry. To adjust for age-and growth-related changes in ventricular mechanics, all echocardiographic variables were expressed as a Z-score relative to the normal distribution. In addition, the smallest diameter of the aorta was assessed by magnetic resonance imaging and calculated as percent narrowing compared with the diameter of the aorta at the diaphragmatic level. In the study group, 24 of 40 patients (60%) had normal LV geometry. Among the 16 patients (40%) with abnormal LV geometry, 5 (12.5%) had a pattern of concentric remodeling and 11 (27.5%) an eccentric hypertrophy. LV hypertrophy was marked (LV mass index >51 g/m2.7) in 5 of these patients. No patient had a pattern of concentric hypertrophy. LV contractility was increased (Z-score >95th percentile) in 28 patients (70%) as assessed using the endocardial stress-velocity index. In contrast, LV contractility assessed using midwall stress-velocity index remained elevated (Z-score >95th percentile) in 15 patients (37.5%). The stepwise multiple logistic regression analysis was not able to detect any significant independent predictor of abnormal LV remodeling, including sex, age at surgical repair, length of postoperative follow-up, heart rate, body mass index, systolic and diastolic blood pressure, and smallest diameter of the aorta, as well as indexes of LV geometry (shape, mass, volume, mass/ volume ratio) and function (preload, afterload, pump function, and myocardial contractility). Thus, normotensive patients after surgical repair of aortic coarctation may be in an LV hyperdynamic cardiovascular state (more frequent in those who have undergone late repair) and have multiple patterns of LV geometry.     

Left ventricular filling is usually normal in uncomplicated coronary disease

Abnormalities in left ventricular filling have been described as an early finding in coronary artery disease (CAD) and more recently, in hypertension (HTN). The present study was undertaken to compare the prevalence and pattern of diastolic dysfunction in these two entities. Three groups of patients were studied: 10 normal volunteers (NLS), 39 HTN patients, and 30 CAD patients. The CAD patients were divided into two subgroups--one with normal ejection fraction (mean 0.60 +/- 0.06) and the second with either a depressed ejection fraction (EF) or a history of HTN (mean EF 0.44 +/- 0.15). The diastolic indices examined were peak filling rate (PFR, in end-diastolic volume [EDV]/sec), time to peak filling rate (TPFR, in msec), and first-third filling fraction (FF 1/3, in sec-1). The PFR in CAD and HTN was significantly reduced (1.86 +/- 0.63 and 2.29 +/- 0.49 vs 2.70 +/- 0.35 EDV/sec in NLS, p less than 0.025 and p less than 0.001, respectively), with the CAD group also being significantly lower than the HTN group (p less than 0.005). TPFR was prolonged in HTN, but not in CAD. FF 1/3 was reduced in both HTN and CAD (0.38 +/- 0.11 and 0.50 +/- 0.14 vs 0.61 +/- 0.06 sec-1 in NLS, p less than 0.001 and p less than 0.025, respectively), but it was significantly lower in HTN than in CAD (p less than 0.001). However, when the subgroup of CAD patients with normal global systolic function was examined separately, diastolic indices were only slightly depressed. More importantly, only one, two, and five patients had PFR, TPFR, and FF 1/3, respectively, which were below the normal values of our laboratory.     

Left ventricular mechanics related to the local distribution of oxygen demand throughout the wall

The complex interactions between left ventricular mechanics and the oxygen demand is studied by relating the left ventricular transmural oxygen demand to the myocardial structural and dynamic characteristics. The study utilizes a recent model of left ventricular contraction, which is based on a nested shell spheroidal geometry, a fan-like fibrous structure, the twisting motion of the left ventricle over its long axis, a transmural electrical activation propagation and the basic laws of sarcomere dynamics. The local "axial" stress (in the direction of the fibers) and the instantaneous sarcomere length are used to calculate the spatial distribution of the intramural oxygen demand per beat Vo2(y), where y is the distance from the endocardium. The normalized local sarcomere stress-length area SLAn(y) is related linearly to Vo2(y) by: Vo2(y) = K1 X SLAn(y) + K2, where K1 and K2 are constants. The calculations show a transmural metabolic gradient which is characterized by higher values of Vo2(y) in the endocardial layers than in the epicardial layers. Shorter endocardial sarcomeres and the twisting motion of the left ventricle around the long axis decrease the metabolic gradient across the wall, while a slow transmural electrical propagation wave as well as a wider angle of distribution of the fan-like fiber architecture increases the transmural metabolic gradient. Integration of the local oxygen demand across the left ventricular wall yields global values in agreement with those based on Suga's pressure-volume area approach. The model thus provides a qualitative and quantitative tool to assess the relation of the local and global oxygen demand to the complex left ventricular structure, fiber mechanics, and the dynamics of contraction.     

Left ventricular bands. A normal anatomical feature.

Discrete delicate fibromuscular structures crossing the cavity of the left ventricle were identified on morphological examination in 329 (48%) of 686 hearts from patients of all ages with congenital heart disease, acquired heart disease, or normal hearts. These structures were also present in 151 (95%) of 159 hearts from animals of six species. Cross sectional echocardiographic findings compatible with these structures were obtained in 39 (21.7%) of 179 children reviewed retrospectively and in three of 800 (0.4%) adults studied prospectively. These structures appear to be a normal anatomical finding.