Myocardial contractile reserve as prognostic determinant in patients with idiopathic dilated cardiomyopathy without overt heart failure

Suppression of lusitropy as a disease mechanism in cardiomyopathies

In cardiac muscle the action of adrenaline on β1 receptors of heart muscle cells is essential to adjust cardiac output to the body's needs. Adrenergic activation leads to enhanced contractility (inotropy), faster heart rate (chronotropy) and faster relaxation (lusitropy), mainly through activation of protein kinase A (PKA). Efficient enhancement of heart output under stress requires all of these responses to work together. Lusitropy is essential for shortening the heartbeat when heart rate increases. It therefore follows that, if the lusitropic response is not present, heart function under stress will be compromised. Current literature suggests that lusitropy is primarily achieved due to PKA phosphorylation of troponin I (TnI) and phospholamban (PLB). It has been well documented that PKA-induced phosphorylation of TnI releases Ca2+ from troponin C faster and increases the rate of cardiac muscle relaxation, while phosphorylation of PLB increases SERCA activity, speeding up Ca2+ removal from the cytoplasm. In this review we consider the current scientific evidences for the connection between suppression of lusitropy and cardiac dysfunction in the context of mutations in phospholamban and thin filament proteins that are associated with cardiomyopathies. We will discuss what advances have been made into understanding the physiological mechanism of lusitropy due to TnI and PLB phosphorylation and its suppression by mutations and we will evaluate the evidence whether lack of lusitropy is sufficient to cause cardiomyopathy, and under what circumstances, and consider the range of pathologies associated with loss of lusitropy. Finally, we will discuss whether suppressed lusitropy due to mutations in thin filament proteins can be therapeutically restored.

Left ventricular contractile reserve as a determinant of adverse clinical outcomes: a systematic review

An abnormal left ventricular contractile reserve is often seen in patients undergoing stress echocardiogram and may indicate the presence of obstructive coronary artery disease. The techniques and indexes used to identify abnormal left ventricular contractile response and its prognostic value in the absence of known causes has not been well studied. To describe the characteristics and clinical outcomes associated with an abnormal left ventricular contractile response, we performed a systematic review that identified 27 eligible studies. A diverse range of indices were utilised to measure left ventricular contractile reserve, most commonly Δleft ventricular ejection fraction in 11 studies. Dobutamine stress echocardiogram was the most commonly performed modality (19 studies) followed by exercise stress echocardiogram (4 studies), dipyridamole stress echocardiogram (2 studies), invasive hemodynamic measurement (1 study) and dobutamine stress magnetic resonance imaging (1 study). All but one study demonstrated a significant association between the absence of left ventricular contractile reserve and increased rate of cardiovascular events, cardiac death and all-cause mortality.

Exercise Cardiac Magnetic Resonance Imaging in Boys With Duchenne Muscular Dystrophy Without Cardiac Disease

BACKGROUND

Duchenne muscular dystrophy is caused by mutations in the DMD gene, resulting in cardiomyopathy in all affected children by 18 years. Although cardiomyopathy is now the leading cause of mortality in these children, there is ongoing debate regarding timely diagnosis, secondary prevention, and treatment of this condition. The purpose of this study was to use exercise cardiac magnetic resonance imaging in asymptomatic young boys with Duchenne muscular dystrophy to describe their heart function and compare this with healthy controls.

METHODS

We studied 11 boys with Duchenne muscular dystrophy aged 8.6 to 13.9 years and 11 healthy age- and sex-matched controls.

RESULTS

Compared with the controls, boys with Duchenne muscular dystrophy had lower ejection fraction at rest (57% versus 63%; P = 0.004). During submaximal exercise, they reached similar peak tachycardia but increased their heart rate and cardiac output only half as much as controls (P = 0.003 and P = 0.014, respectively). End-systolic volume remained higher in boys with Duchenne muscular dystrophy both at rest and during exercise. When transthoracic echocardiography was compared with cardiac magnetic resonance imaging, 45% of the echocardiograms had suboptimal or poor views in the Duchenne muscular dystrophy group.

CONCLUSIONS

Boys with Duchenne muscular dystrophy had abnormalities in left ventricular systolic function that were exaggerated by exercise stress. Exercise cardiac magnetic resonance imaging is feasible in a select population of children with Duchenne muscular dystrophy, and it has the potential to unmask early signs of cardiomyopathy.

Assessing the future risks of subsequent pregnancies in peripartum cardiomyopathy

Peripartum cardiomyopathy is a myocardial disease process which occurs in young women either in late pregnancy or the early postpartum period. Due to the young age of women effected by this disease, many of these patients elect to pursue a subsequent pregnancy after their initial diagnosis. Currently, echocardiography is used to better elucidate the cardiovascular risks these young patients face when undergoing a subsequent pregnancy; however, the most accurate modality to determine these risks is debatable. In this review, we explore the current literature regarding the use and accuracy of resting transthoracic echocardiography, exercise stress echocardiography, and dobutamine stress echocardiography in risk stratification of a subsequent pregnancy in a patient with peripartum cardiomyopathy.

Differentiation between athlete’s heart and dilated cardiomyopathy in athletic individuals

Objective

Distinguishing early dilated cardiomyopathy (DCM) from physiological left ventricular (LV) dilatation with LV ejection fraction <55% in athletes (grey zone) is challenging. We evaluated the role of a cascade of investigations to differentiate these two entities.

Methods

Thirty-five asymptomatic active males with DCM, 25 male athletes in the ‘grey zone’ and 24 male athletes with normal LV ejection fraction underwent N-terminal pro-brain natriuretic peptide (NT-proBNP) measurement, ECG and exercise echocardiography. Grey-zone athletes and patients with DCM underwent cardiovascular magnetic resonance (CMR) and Holter monitoring.

Results

Larger LV cavity dimensions and lower LV ejection fraction were the only differences between grey-zone and control athletes. None of the grey-zone athletes had abnormal NT-proBNP, increased ectopic burden/complex arrhythmias or pathological late gadolinium enhancement on CMR. These features were also absent in 71%, 71% and 50% of patients with DCM, respectively. 95% of grey-zone athletes and 60% of patients with DCM had normal ECG. During exercise echocardiography, 96% grey-zone athletes increased LV ejection fraction by >11% from baseline to peak exercise compared with 23% of patients with DCM (p<0.0001). Peak LV ejection fraction was >63% in 92% grey-zone athletes compared with 17% patients with DCM (p<0.0001). Failure to increase LV ejection fraction >11% from baseline to peak exercise or achieve a peak LV ejection fraction >63% had sensitivity of 77% and 83%, respectively, and specificity of 96% and 92%, respectively, for predicting DCM.

Conclusion

Comprehensive assessment using a cascade of routine investigations revealed that exercise stress echocardiography has the greatest discriminatory value in differentiating between grey-zone athletes and asymptomatic patients with DCM. Our findings require validation in larger studies.

The Utility of Cardiac Reserve for the Early Detection of Cancer Treatment-Related Cardiac Dysfunction: A Comprehensive Overview

With progressive advancements in cancer detection and treatment, cancer-specific survival has improved dramatically over the past decades. Consequently, long-term health outcomes are increasingly defined by comorbidities such as cardiovascular disease. Importantly, a number of well-established and emerging cancer treatments have been associated with varying degrees of cardiovascular injury that may not emerge until years following the completion of cancer treatment. Of particular concern is the development of cancer treatment related cardiac dysfunction (CTRCD) which is associated with an increased risk of heart failure and high risk of morbidity and mortality. Early detection of CTRCD appears critical for preventing long-term cardiovascular morbidity in cancer survivors. However, current clinical standards for the identification of CTRCD rely on assessments of cardiac function in the resting state. This provides incomplete information about the heart's reserve capacity and may reduce the sensitivity for detecting sub-clinical myocardial injury. Advances in non-invasive imaging techniques have enabled cardiac function to be quantified during exercise thereby providing a novel means of identifying early cardiac dysfunction that has proved useful in several cardiovascular pathologies. The purpose of this narrative review is (1) to discuss the different non-invasive imaging techniques that can be used for quantifying different aspects of cardiac reserve; (2) discuss the findings from studies of cancer patients that have measured cardiac reserve as a marker of CTRCD; and (3) highlight the future directions important knowledge gaps that need to be addressed for cardiac reserve to be effectively integrated into routine monitoring for cancer patients exposed to cardiotoxic therapies.

Contractile reserve as a predictor of prognosis in patients with non-ischaemic systolic heart failure and dilated cardiomyopathy: a systematic review and meta-analysis

Objective

Patients with non-ischaemic systolic heart failure (HF) and idiopathic dilated cardiomyopathy (DCM) are a heterogenous group with varied morbidity and mortality. Prognostication in this group is challenging. We performed a systematic review and meta-analysis to examine the significance of the presence of contractile reserve as assessed via stress imaging on mortality and hospitalisation.

Methods

A search for studies that non-invasively assessed contractile reserve in patients with DCM or non-ischaemic HF with reduced ejection fraction, stress imaging with follow-up data comparing outcomes. A range of imaging modalities and stressors were included. We examined primary endpoints of mortality and secondary endpoints of combined cardiovascular events including HF progression or hospitalisation. Our analysis compared endpoints in patients with contractile reserve and those without it.

Results

Nine prospective cohort studies were identified describing a total of 787 patients. These studies are methodologically but not statistically heterogenous (I² = 31%). Using a random effect model, the presence of contractile reserve was associated with a significantly lower risk of mortality and cardiovascular events odds ratios of 0.20 (CI 0.11, 0.39) (P < 0.00001) and 0.13 (CI 0.04, 0.40) (P = 0.0004), respectively.

Conclusion

Regardless of stressor and imaging modality and despite the significant methodological heterogeneity within the current data (imaging techniques and parameters), patients with non-ischaemic cardiomyopathy and reduced EF who demonstrate contractile reserve have a lower mortality, and lower events/hospitalisations. The presence of contractile reserve therefore offers a potential positive prognostic indicator when managing these patients.

Temporal changes in plasma brain natriuretic peptide levels during exercise stress-echocardiography in patients with dilated cardiomyopathy

The aim of this study was to evaluate temporal changes in brain natriuretic petide (BNP) levels during exercise stress-echocardiography in patients with dilated cardiomyopathy with respect to the left ventricular contractile reserve. We studied 55 consecutive patients with dilated cardiomyopathy (mean age, 55 ± 10 years, 49 (89.1%) male). All patients underwent exercise stress-echocardiography on a treadmill using the modified Bruce protocol. Contractile reserve was assessed by measuring changes in the wall motion score index (ΔWMSI) at rest and and at peak exercise. Levels of BNP were measured at rest, in the first minute, and after 20 minutes following termination of the stress test. Thirty-six patients had preserved left ventricular contractile reserve and 19 patients did not. Patients with preserved left ventricular contractile reserve showed a continuous rise in BNP levels from baseline to peak exercise and to 20 minutes following exertion (83.95 ± 108.51 versus 105.89 ± 116.00 versus 110.95 ± 119.70 ng/L, P < 0.001, respectively). On the other hand, patients without preserved left ventricular contractile reserve showed a decline in BNP levels at peak exercise as compared to baseline (335.49 ± 693.11 versus 320.08 ± 562.60 P = 0.031). ΔBNP was positively correlated with preserved contractile reserve (r = 0.46, P = 0.03) and lower NYHA class (r = -0.65, P = 0.001) in patients in whom baseline LVEF was lower than 20%. Multivariate analysis identified only WMSI at rest (beta -3.365, P = 0.008, 95 CI 0.03 to 0.411) as an independent predictor of left ventricular contractile reserve.The increase in BNP levels during exercise stress-echocardiography is associated with preserved left ventricular contractile reserve in patients with dilated cardiomyopathy.

Feasibility of semi-quantitative assessment of left ventricular contractile reserve in dilated cardiomyopathy

BACKGROUND

We and others have shown previously that left ventricular (LV) contractile reserve assessed quantitatively by high-dose dobutamine stress-echocardiography (DSE) has prognostic implications in patients with dilated cardiomyopathy.

PURPOSE

To assess the feasibility of semi-quantitative assessment of LV contractile reserve by differently skilled operators in patients with dilated cardiomyopathy.

METHODS

High-dose DSE was performed in 63 consecutive patients, mean age 50 ± 10 years and ejection fraction (EF) 19 ± 8%. LVEF was calculated 1) using Simpson's biplane formula, and 2) semi-quantitatively (5% increments) by novice and experienced echocardiographers, and by a DSE expert. Patients were considered to have preserved LV contractile reserve if LVEF dobutamine-induced change was ≥5%.

RESULTS

Twenty-seven (45.8%) patients died during the 5-year follow-up. The feasibility of the assessment was 89%, 94%, and 98% for novice and experienced readers and DSE expert, respectively. Kaplan-Meier analysis showed that LV contractile reserve assessed semi-quantitatively by DSE expert and experienced reader achieved the best prognostic separation (log rank 19.63 and 18.99, respectively, p < 0.001 for both), followed by quantitative assessment (log rank 9.76, p = 0.0018) and assessment by novice reader (log rank 8.76, p = 0.012). Areas under the curves were similar for quantitative and semi-quantitative assessment of LV contractile reserve.

CONCLUSIONS

Our data indicate that semi-quantitative assessment of LV contractile reserve is feasible by differently skilled operators.

Effect of pimobendan on the clinical outcome and survival of cats with non-taurine responsive dilated cardiomyopathy

This retrospective study was designed to assess the effect of pimobendan on the median survival time (MST) of cats with non-taurine responsive dilated cardiomyopathy (DCM). Thirty-two client-owned cats with a left ventricular internal dimension at end systole (LVIDs) >14 mm, a fractional shortening (FS) <28% and a lack of response to taurine therapy were included over a 9-year period (2001-2010). These cats were divided into pimobendan (n=16) and non-pimobendan (n=16) treatment groups. All cats received standard treatment with frusemide, taurine and benazepril or enalapril. Nine cats in the non-pimobendan group also received digoxin. The MST of the pimobendan group (49 days; range 1 to >502 days) was four times that of the non-pimobendan group (12 days; 1 to 244 days). The difference in survival between the two groups was statistically significant (P = 0.048). Hypothermia and FS <20% were associated with a poor prognosis. No adverse effects to pimobendan were noted.

Resting measures and physiological responses to exercise for the determination of prognosis in patients with chronic heart failure: useful tools for clinical decision-making

Despite recent advances in the management of chronic heart failure (CHF), the prognosis of many of these patients remains dire. The need for an accurate prognosis in these patients has led to the identification of several indicators purported to represent the impact of the disease. Such indicators often are obtained at rest and are not always accurate at determining the clinical status of CHF patients. As a result, the relationship between prognostic indicators and clinical outcomes is frequently weak. On the other hand, physiological responses to acute exercise may unmask patients with the worst clinical status and identify those at increased risk of poor outcomes. Therefore, the present review appraises the value of several prognostic indicators for patients with CHF collected at rest and in response to exercise. In particular, it contrasts the value and accuracy of predictors of mortality widely used in clinical settings, such as oxygen uptake, ventilatory efficiency, and left ventricular ejection fraction, with new and more direct indicators of ventricular systolic and diastolic function.

Loss of diastolic time as a mechanism of exercise-induced diastolic dysfunction in dilated cardiomyopathy

BACKGROUND

Cardiac performance can be characterized in terms of the relative duration of left ventricular systole and diastole. Little is known about exercise-induced abnormalities of the systolic-diastolic phase proportion and its impact on hemodynamic variables in patients with idiopathic dilated cardiomyopathy (IDCM).

METHODS

The phases of the cardiac cycle were derived with high temporal resolution from the left ventricular time-activity curve simultaneous with hemodynamic measurements. In patients with IDCM, the loss of diastolic time (LDT) per beat was quantified using a regression equation obtained from a healthy control group (n = 26). According to the median LDT at peak exercise, patients were divided into 2 subgroups: subgroup A with an LDT <or=22 milliseconds (n = 28) and subgroup B with an LDT >22 milliseconds (n = 27).

RESULTS

The relative duration of left ventricular systole was increased in patients with IDCM during peak exercise compared to healthy subjects (29.3 vs 26.7 s/min, P < .02). This abnormality translated into a significant LDT when observed, and predicted values of diastolic time were compared. Subgroup B patients had a higher increment in mean pulmonary capillary wedge pressure but a smaller increase in stroke volume index from rest to peak exercise (14.3 vs 8.6 mm Hg [P = .007] and 12.5 vs 7.2 mL/m(2) [P = .04]) compared to subgroup A patients.

CONCLUSION

An abnormal shortening of diastolic time during exercise can restrict left ventricular filling to an extent that is sufficient to limit left ventricular stroke volume reserve and to cause pulmonary congestion.

Negative stress echo: Further prognostic stratification with assessment of pressure–volume relation

BACKGROUND

A maximal negative stress echo identifies a low risk for subsequent hard events subset. However, the potentially prognostically relevant information on global contractile reserve on the left ventricle is missed by standard regional wall motion assessment, and can be obtained by end-systolic pressure-volume relationship (PVR) evaluation.

AIM

To assess the relative prognostic value of PVR in patients with negative stress echo.

METHODS

We enrolled 99 consecutive patients (age=61+/-14 years; 81 males, LVEF 47+/-14%, WMSI=1.42+/-0.50) with negative exercise stress echo for standard wall motion criteria. To build the PVR, the force was determined at rest and peak stress as the ratio of the systolic pressure/end-systolic volume index. All patients were followed-up on medical therapy.

RESULTS

Median follow-up was 21 months (interquartile range 12-26). Twenty-nine events have been observed: 6 deaths, 10 heart failure related hospitalization and 13 worsening NYHA class of >or=1 grade. Using Cox's proportional hazard model the best independent predictor of total events was SP/ESV index change (rest-stress) <1.5 mm Hg/ml/m(2) as determined by ROC analysis cut-off (RR=29, p=0.001, sensitivity=80%, specificity=93%). The overall survival and event-free survival was 34% in patients with change (rest-stress) SP/ESV index<1.5 mm Hg/ml/m(2) and 97% in whose with >1.5 mm Hg/ml/m(2).

CONCLUSIONS

In patients with negative stress echo, a preserved global contractility response can be easily identified through stress-induced variation in SP/ESV index, with powerful further risk stratification.

The independent prognostic value of contractile and coronary flow reserve determined by dipyridamole stress echocardiography in patients with idiopathic dilated cardiomyopathy

The aim of this study was to evaluate the prognostic value of Doppler echocardiographically derived coronary flow reserve (CFR) in assessing inotropic response in patients with idiopathic dilated cardiomyopathy (IDC). One hundred thirty-two patients with IDC (90 men; mean age 62 +/- 11 years) were evaluated by transthoracic dipyridamole (0.84 mg/kg in 10 minutes) stress echocardiography. All patients had ejection fractions <40% (mean 33 +/- 7%) and angiographically normal coronary arteries, with New York Heart Association class <or=III. CFR was assessed in the left anterior descending coronary artery by pulsed Doppler as the ratio of maximal peak vasodilation (dipyridamole) to rest diastolic flow velocity. Inotropic reserve was identified as rest-stress variation in wall motion score index >0.25. All patients were followed for a median of 24 months. Mean CFR was 2.0 +/- 0.5. On individual patient analysis, 48 patients had normal CFR (>2), and 84 had abnormal CFR. The mean wall motion score index at rest was 2.0 +/- 0.33 and decreased to 1.8 +/- 0.4 at peak dipyridamole dose (p <0.000). Forty-two patients (32%) had inotropic reserve. During follow-up, 19 patients died, and 34 showed worsening of New York Heart Association class. The worst outcomes were observed in those patients with abnormal CFR and no inotropic reserve with high-dose dipyridamole. In a Cox model, mitral insufficiency (hazard ratio [HR] 1.7, 95% confidence interval [CI] 1.1 to 2.8), New York Heart Association class (HR 2.0, 95% CI 1.1 to 3.7), abnormal CFR (HR 2.8, 95% CI 1.0 to 8.5), wall motion score index at rest (HR 3.5, 95% CI 1.3 to 9.8), and the absence of inotropic reserve with high-dose dipyridamole (HR 2.3, 95% CI 1.06 to 5.1) were independent predictors of survival. In conclusion, in patients with IDC, CFR is often impaired. Reduced CFR and the absence of an inotropic response during vasodilator stress are additive in predicting a worse prognosis.

Head-to-head comparison of indices of left ventricular contractile reserve assessed by high-dose dobutamine stress echocardiography in idiopathic dilated cardiomyopathy: five-year follow up

OBJECTIVE

To compare head to head the indices of left ventricular contractile reserve assessed by high-dose dobutamine in the five-year prognosis of patients with idiopathic dilated cardiomyopathy.

DESIGN AND SETTING

Prospective study in a tertiary care centre.

PATIENTS

63 consecutive patients with idiopathic dilated cardiomyopathy.

INTERVENTIONS

High-dose dobutamine stress echocardiography was performed in progressive stages lasting 5 min each. Wall motion score index, ejection fraction, cardiac power output and end systolic pressure to volume ratio were evaluated as indices of left ventricular contractility.

MAIN OUTCOME MEASURE

Five-year cardiac mortality.

RESULTS

During the follow up of 59 patients, 27 (45.8%) died of cardiac causes. According to Kaplan-Meier and receiver operating characteristic analyses all indices of contractile reserve differentiated patients with respect to cardiac death. Wall motion score index achieved the best separation (log rank 21.75, p < 0.0001, area under the curve 0.84), followed by change in ejection fraction (log rank 11.25, p = 0.0008, area under the curve 0.79), end systolic pressure to volume ratio (log rank 14.32, p = 0.0002, area under the curve 0.75) and cardiac power output (log rank 9.84, p = 0.0017, area under the curve 0.71). Cox's regression model identified wall motion score index as the only independent predictor of cardiac death.

CONCLUSIONS

These data show that all examined indices of left ventricular contractile reserve are predictive of five-year prognosis, but change in wall motion score index may have the greatest prognostic potential.

Cardiac sympathetic dysfunction correlates with abnormal myocardial contractile reserve in dilated cardiomyopathy patients

OBJECTIVES

We investigated the relationship between iodine-123-metaiodobenzylguanidine (123I-MIBG) findings and myocardial contractile reserve in patients with mild to moderate dilated cardiomyopathy (DCM).

BACKGROUND

Little is known regarding the relationship between cardiac sympathetic nervous function and myocardial contractile reserve in DCM.

METHODS

Twenty-four DCM patients who showed sinus rhythm underwent echocardiography, biventricular catheterization, and myocardial 123I-MIBG scintigraphy. Left ventricular (LV) pressures were measured using a micromanometer-tipped catheter. The myocardial contractile function (LV dP/dt(max)) was determined at rest and during atrial pacing. The messenger ribonucleic acid (mRNA) expressions of intracellular Ca2+-regulatory proteins were analyzed by real-time quantitative reverse transcription-polymerase chain reaction. Myocardial 123I-MIBG accumulation was quantified as a heart-mediastinum ratio (HMR).

RESULTS

A significant correlation was observed between the delayed 123I-MIBG HMR and the percentage change in LV dP/dt(max) from the baseline to the peak or critical heart rate (r = 0.64; p < 0.001). The delayed 123I-MIBG HMR was significantly lower in patients showing a worsening change in LV dP/dt(max) than in those showing a favorable change (p < 0.005). The maximum LV dP/dt(max) during pacing and the sarcoplasmic reticulum Ca2+-ATPase (SERCA2) mRNA levels were significantly more reduced in patients with a delayed HMR < or =1.8 than in those with a delayed HMR >1.8 (p < 0.05, respectively).

CONCLUSIONS

Abnormal myocardial 123I-MIBG accumulation is related to an impaired myocardial contractile reserve and down-regulation of SERCA2 mRNA in DCM. Myocardial 123I-MIBG scintigraphy can be useful in noninvasively evaluating myocardial contractile reserve in patients with mild to moderate DCM.

Relation of myocardial histomorphometric features and left ventricular contractile reserve assessed by high-dose dobutamine stress echocardiography in patients with idiopathic dilated cardiomyopathy

BACKGROUND

This study was designed to determine the relationship between histomorphometric features and contractile reserve assessed by high-dose dobutamine stress echocardiography in patients with idiopathic dilated cardiomyopathy.

METHODS

Twenty-four consecutive patients (21 men, aged 43.4+/-8.7 years) with idiopathic dilated cardiomyopathy underwent dobutamine stress echocardiography. Wall motion score index, ejection fraction, cardiac power output and end-systolic pressure/volume ratio were used as indices of left ventricular contractility. Left ventricular endomyocardial biopsy specimens (3-5 per patient) were routinely processed and stained with Masson trichrome, interstitial fibrosis and myocyte diameter were calculated quantitatively.

RESULTS

Myocyte diameter and interstitial fibrosis showed strongest correlation with change in wall motion score index (r=-0.667, p<0.001, and r=-0.567, p=0.004, respectively), followed by change in ejection fraction (r=-0.603, p=0.002, and r=-0.467, p=0.021, respectively). Interstitial fibrosis showed no correlation with change of cardiac power output and end-systolic pressure/volume ratio, whereas myocyte diameter was associated with change of both indices (r=-0.565, p=0.004, and r=-0.455, p=0.025).

CONCLUSIONS

Contractile reserve elicited by high-dose dobutamine is strongly related to the degree of histological disruption in patients with idiopathic dilated cardiomyopathy.

Stress-echocardiography in idiopathic dilated cardiomyopathy: instructions for use

A number of studies have suggested that stress-echocardiography may be used for prognostic stratification in patients with idiopathic dilated cardiomyopathy. There is no consensus on which protocol or which measurements of left ventricular contractile reserve to use. The most frequently used protocol is low-dose dobutamine stress-echocardiography, and most commonly used measures of left ventricular systolic performance are ejection fraction, wall motion score index and cardiac power output.Stress-echocardiography has been shown to predict improvement in cardiac function in patients with recently diagnosed dilated cardiomyopathy, as well as to predict which patients will benefit from the treatment with beta-blockers. Most importantly, stress-echocardiography can identify patients with worse prognosis in terms of cardiac death and need for transplantation. Additionally, contractile reserve is closely correlated with maximal oxygen consumption and can even be used for further stratification in patients with maximal oxygen consumption between 10 and 14 ml/kg/min. Future studies are needed for head-to-head comparison of various protocols in an attempt to make standardization in the assessment of patients with dilated cardiomyopathy.

Stress echocardiography in heart failure

Echocardiography has the ability to noninvasively explore hemodynamic variables during pharmacologic or exercise stress test in patients with heart failure. In this review, we detail some important potential applications of stress echocardiography in patients with heart failure. In patients with coronary artery disease and chronic LV dysfunction, dobutamine stress echocardiography is able to distinguish between viable and fibrotic tissue to make adequate clinical decisions. Exercise testing, in combination with echocardiographic monitoring, is a method of obtaining accurate information in the assessment of functional capacity and prognosis. Functional mitral regurgitation is a common finding in patients with dilated and ischaemic cardiomyopathy and stress echocardiography in the form of exercise or pharmacologic protocols can be useful to evaluate the behaviour of mitral regurgitation. It is clinical useful to search the presence of contractile reserve in non ischemic dilated cardiomyopathy such as to screen or monitor the presence of latent myocardial dysfunction in patients who had exposure to cardiotoxic agents. Moreover, in patients with suspected diastolic heart failure and normal systolic function, exercise echocardiography could be able to demonstrate the existence of such dysfunction and determine that it is sufficient to limit exercise tolerance. Finally, in the aortic stenosis dobutamine echocardiography can distinguish severe from non-severe stenosis in patients with low transvalvular gradients and depressed left ventricular function.

Myocardial contractile reserve under low doses of dobutamine and improvement of left ventricular ejection fraction with treatment by carvedilol

To examine the ability of myocardial contractile reserve (MCR) assessment to predict the improvement of left ventricular ejection fraction with treatment by carvedilol, a prospective study was undertaken in 85 patients with chronic heart failure and left ventricular ejection fraction < 45%. Low dose dobutamine echocardiography (DSE), a 6-min walk test and measured brain natriuretic peptide (BNP) were assessed in all the patients. Patients were separated into two groups. Group A were patients without any myocardial reserve and group B patients with a myocardial contractile reserve defined as an increment of more than 20% of the resting left ventricular ejection fraction during dobutamine infusion. The two groups differed for percentage of ischemic cardiomyopathy (67.8 in group A vs. 29.7% in group B P = 0.028), 6-min walk test performance (respectively, 343 vs. 415 meters P < 0.05) and BNP plasma levels (respectively, 184.5 vs. 70.1 P < 0.02) but not for left ventricular ejection fraction or NYHA class. During DSE, MCR and heart rate variation was higher in group B than in group A. At the end of the follow up, LVEF increased and NYHA class decreased in group B but not in group A. In multivariate analysis the existence of MCR could predict the improvement of LVEF with treatment by carvedilol. In our study, studying MCR could help to predict patients who will improve their LVEF with carvedilol prior to the administration of the treatment.

Prognostic value of low-dose dobutamine echocardiography in patients with idiopathic dilated cardiomyopathy

STUDY OBJECTIVES

Dobutamine echocardiography is widely used for the evaluation of myocardial contractile reserve. The purpose of the study was to determine the prognostic value of low-dose dobutamine echocardiography in patients with idiopathic dilated cardiomyopathy (IDCM).

PATIENTS

The study group consisted of 77 consecutive patients with recently diagnosed IDCM (mean [+/- SD] age, 49 +/- 9 years; men, 82%) and left ventricular (LV) ejection fractions of < 40%.

INTERVENTIONS

Two-dimensional and Doppler echocardiographic variables were measured before and after the infusion of dobutamine at the rate of 10 microg/kg/min for 5 min.

MEASUREMENTS AND RESULTS

During a mean follow-up period of 63 +/- 7 months (range, 49 to 75 months) 30 patients (39%) died and five patients (6%) underwent successful heart transplantations. Using multivariate regression analysis, the only significant factors related to fatal outcome or the need for cardiac transplantation were the following: (1) LV end-systolic volume of > 150 mL after low-dose dobutamine infusion (odds ratio [OR], 2.2; confidence interval [CI], 1.2 to 4.1; p = 0.011); (2) no decrease of LV end-diastolic volume after dobutamine infusion (OR, 1.9; CI, 1.1 to 3.4; p = 0.031); (3) atrial fibrillation (OR, 2.7; CI, 1.4 to 5.3; p = 0.003); and (4) male gender (OR, 2.6; CI, 1.2 to 5.5; p = 0.017). A scoring system was proposed with one point assigned for each of the above-mentioned factors. The mortality rates for total scores of 0, 1, 2, 3, and 4 were 0%, 19%, 48%, 83%, and 100%, respectively.

CONCLUSION

The response of the LV to low-dose dobutamine infusion adds clinically valuable prognostic information to the evaluation of the patient with IDCM.

Adynamic cardiomyoplasty: effect on cardiac efficiency and contractile reserve in dogs with adriamycin-induced cardiomyopathy

The girdling effect of the skeletal muscle wrap seems to be the primary mechanism of action of cardiomyoplasty. It is associated with a myocardial sparing effect. Myocardial sparing effect has been shown with an active muscle wrap or an active muscle wrap acutely turned "OFF". The purpose of the study was to evaluate the effect of a passive skeletal muscle wrap on cardiac energetics parameters and contractile reserve in a canine model of cardiomyopathy. Six dogs with adriamycin-induced cardiomyopathy were studied. Three dogs underwent right latissimus dorsi adynamic cardiomyoplasty and 3 served as controls. Cardiac and coronary sinus catheterizations were performed at 0 and 6 weeks. A dobutamine stress test was performed at 6 weeks. Myocardial oxygen consumption was not reduced in the cardiomyoplasty group (139.20+/-86.90 Joules/min) compared to the control group (95.10+/-12.60 Joules/min, P = 0.27) at 6 weeks. Mechanical cardiac efficiency was increased in the cardiomyoplasty group (33.15+/-4.40%) compared to the control group (24.50+/-2.70%, P = 0.049) at 6 weeks. Left ventricular end diastolic diameter index was reduced in the cardiomyoplasty group (38.00+/-1.70 mm/m2) compared to the control group (46.30+/-1.55 mm/m2, P = 0.049) at 6 weeks. Indices of diastolic function -dp/dt, and tau were not significantly affected by adynamic cardiomyoplasty. Max dp/dt was increasing more in the cardiomyoplasty group than in the control group (P = 0.07) during dobutamine stress test. Mechanical cardiac efficiency was better preserved by the adynamic cardiomyoplasty. Myocardial contractile reserve might be better preserved with cardiomyoplasty.

Prognostic significance of the dobutamine echocardiography test in idiopathic dilated cardiomyopathy

Dobutamine stress echo provides potentially useful information on idiopathic dilated cardiomyopathy (IDC). From February 1, 1997, to October 1, 1999, 186 patients (131 men and 55 women, mean age 56 +/- 12 years) with IDC, ejection fraction <35%, and angiographically normal coronary arteries were studied by high-dose (up to 40 micro/kg/min) dobutamine echo in 6 centers, all quality controlled for stress echo reading. In all patients, wall motion score index (WMSI) (from 1 = normal to 4 = dyskinetic in a 16- segment model of the left ventricle) was evaluated by echo at baseline and peak dobutamine. One hundred eighty-four patients were followed up (mean 15 +/- 13 months) and only cardiac death was considered as an end point. There were 29 cardiac deaths. Significant parameters for survival prediction at univariate analysis are: DeltaWMSI (chi-square 20.1; p <0.0000), New York Heart Association (NYHA) class (chi-square 17.57; p <0.0000), rest ejection fraction (chi-square 10.41; p = 0.0013), angiotensin-converting enzyme inhibitors (chi-square 8.23; p = 0.0041), and hypertension (chi-square 8.08, p = 0.0045). In the multivariate stepwise analysis only DeltaWMSI and NYHA were independent predictors of outcome (DeltaWMSI = hazard ratio 0.02, p < 0.0000; NYHA class = hazard ratio 3.83, p < 0.0000). Kaplan-Meier survival estimates showed a better outcome for patients with a large inotropic response (DeltaWMSI > or =0.44, a cutoff identified by receiver-operating characteristic curves analysis) than for those with a small or no myocardial inotropic response to dobutamine (93.6% vs 69.4%, p = 0.00033). Thus, in patients with IDC, an extensive contractile reserve identified by high-dose dobutamine stress echocardiography is associated with a better survival.

Ultrasonic tissue characterization can predict beta-blocker efficacy in dilated cardiomyopathy

The aim was to determine if the combination of cyclic variation of myocardial integrated backscatter (variation IB) and left ventricular mass measurements can predict the efficacy of beta-blocker treatment in dilated cardiomyopathy. In 32 patients, left ventricular mass and variation IB were measured at baseline and during 6 microg/kg/min dobutamine infusion before the initiation of beta-blocker therapy. Variation IB was measured at left and right ventricular halves in the ventricular septum. The baseline left ventricular mass index and transseptal variation IB gradient during dobutamine were significantly greater in the effective group (1.16 +/- 0.18 g/mL and 1.8 +/- 0.6 dB) than in the ineffective group (0.94 +/- 0.28 g/mL, p = 0.032 and 0.4 +/- 0.6 dB, p < 0.005). When both baseline left ventricular mass index > or = 1.05 g/mL and transseptal variation IB gradient during dobutamine > or = 1.5 dB were defined as predictive criteria for the effective group, the sensitivity was 78% and the specificity was 86%. Analysis of transseptal variation IB during dobutamine may provide useful information predicting the efficacy of beta-blocker therapy in dilated cardiomyopathy.

Examination of left ventricular contractile reserve by Doppler myocardial imaging in patients with dilated cardiomyopathy

Detection of left ventricular contractile reserve by means of dobutamine stress echocardiography is a well known technique. The aim of the present study was to detect velocity changes during the administration of dobutamine, to establish if Doppler myocardial imaging is a suitable method for determining left ventricular contractile reserve, and to determine if the technique provides more information than traditional stress echocardiography. Twenty-five patients (all males; mean age, 53.4 years) were examined for a clinical diagnosis of idiopathic dilated cardiomyopathy with a poor left ventricular systolic function (ejection fraction less than 30%). Doses of 5-10 and 20 mg/kg/min dobutamine were administered and elevated at 4-minute intervals. Ejection fraction was calculated using the Simpson rule. The peak systolic and the early and late diastolic velocities were measured in the basal segment of the septum and the inferior wall at baseline and at full dose of dobutamine. Results indicated that peak systolic velocity increased significantly, both in the septum (0.11±0.03 vs. 0.20±0.05 m/sec; p=0.001) and in the inferior wall (0.10±0.05 vs. 0.17±0.06 m/sec; p=0.03). Late diastolic velocities also increased significantly, both in the septum (0.17±0.05 vs. 0.22±0.07 m/sec; p=0.01) and in the inferior wall (0.18±0.08 vs.0.21±0.02 m/sec; p=0.01). There was a significant linear correlation between the relative increases in basal ejection fraction value and in peak systolic velocity upon dobutamine stimulation. Patients were divided into responders and nonresponders based on responses in either ejection fraction (25% relative increase) or peak systolic velocity (5 cm/s increase). This study concludes that 1) Doppler myocardial imaging is an adequate and simple technique to examine left ventricular contractile reserve; and 2) measurement of peak systolic velocity during dobutamine stimulation seems to be a simple and good indicator of left ventricular contractile reserve. (c)2001 CHF, Inc.

Prediction of contractile reserve by cyclic variation of integrated backscatter of the myocardium in patients with chronic left ventricular dysfunction

OBJECTIVE

To clarify whether assessment of the acoustic properties of the myocardium at rest can predict contractile reserve in patients with chronic left ventricular dysfunction.

METHODS

23 patients (mean (SD) age 63 (12) years) with chronic left ventricular dysfunction were studied. The magnitude of cardiac cycle dependent variation of integrated backscatter (CVIB) of the myocardium was measured at rest in the basal and mid segment of the septum and posterior wall of the left ventricle, using a real time two dimensional integrated backscatter imaging system. The results were compared with the percentage wall thickening and the wall motion at rest and during low dose dobutamine infusion. The wall motion was graded as normal, hypokinetic, or akinetic and contractile reserve was considered present when an akinetic or hypokinetic segment improved during dobutamine infusion.

RESULTS

The CVIB at rest correlated with per cent wall thickening at rest and during dobutamine infusion (at rest, r = 0.61, p < 0.0001, during dobutamine, r = 0.76, p < 0.0001). Of the 76 segments examined, 27 showed contractile reserve. The mean CVIB at rest was significantly greater in segments with contractile reserve than in those without (p < 0.0001). CVIB above 3 dB at rest predicted segments with contractile reserve with a sensitivity and specificity of 81% and 60%, respectively (p < 0.0001).

CONCLUSIONS

CVIB reflected not only myocardial contractility but also the functional capacity of the myocardium. It predicted segmental contractile reserve in patients with chronic left ventricular dysfunction.

Current perspectives of partial left ventriculectomy in the treatment of dilated cardiomyopathy

OBJECTIVES

Partial left ventriculectomy has been performed as an alternative to heart transplantation in the treatment of severe cardiomyopathies. This investigation documents the clinical and left ventricular (LV) function effects of this procedure, associated, when necessary, with mitral insufficiency correction, in 43 patients with idiopathic dilated cardiomyopathy.

METHODS

Eighteen patients were in New York Heart Association class III and 25 in class IV. Seven of them were operated in cardiogenic shock. The procedure was associated with mitral annuloplasty in 32 patients and mitral replacement in three.

RESULTS

Nine patients (20.9%) died during the hospital period and the cause of death was associated with ventricular failure in seven patients. The other patients were followed up from 2 to 57 months (mean, 28.3 months). At 6 months of follow-up, eight patients were in functional class I, 13 in class II, three in class III and one patient was in class IV (P<0.001). On the other hand, nine patients died during the first 6 months and another six in the later postoperative period. The cause of late death was progressive heart failure in eight patients, and seven patients died because of arrhythmia related events. The actuarial survival was 58.1+/-7.5% at 1 year and 43.9+/-8.1% at 4 years of follow-up. Regarding ventricular function modifications, the LV diastolic volume decreased by around 25% and the LV ejection fraction increased from 17.8+/-4.7 to 22.3+/-7.9% (P<0.001), whereas significant changes in the cardiac index, stroke index and pulmonary pressures were also found 1 month after the operation. In the later follow-up, despite the maintenance of hemodynamic improvement, the LV diastolic volume tended to increase and returned to preoperative levels at 4 years, while a concomitant decrease in the LV ejection fraction was also observed.

CONCLUSION

Partial left ventriculectomy associated with mitral insufficiency correction improves LV function and ameliorates congestive heart failure in patients with idiopathic cardiomyopathy. Otherwise, the LV function benefits seem to be restricted by the possibility of progressive LV redilatation. Furthermore, the clinical application of this procedure is limited by the high mortality observed in the first postoperative months and by the possibility of heart failure progression and arrhythmia related events at late follow-up.

Myocardial contractile reserve on dobutamine echocardiography predicts late spontaneous improvement in cardiac function in patients with recent onset idiopathic dilated cardiomyopathy

OBJECTIVES

The purpose of this study was to determine whether identification of contractile reserve with dobutamine would predict recovery of myocardial function during follow-up in patients with recent onset idiopathic dilated cardiomyopathy (IDC).

BACKGROUND

The prognosis of patients presenting with new onset IDC is variable and difficult to predict.

METHODS

Twenty-two patients (17 men, 5 women, 46 +/- 14 years) with recently diagnosed IDC (4 +/- 3 months) underwent dobutamine echocardiography. Left ventricular ejection fraction (LVEF) and LV sphericity before and at peak dobutamine infusion (30 +/- 11 microg/kg/min) were determined. A follow-up echocardiographic assessment was done at 6 +/- 4 months.

RESULTS

The LVEF on dobutamine was directly related to baseline LV mass expressed as g/ml (Pearson r = 0.65, p = 0.0003). Baseline variables that were significantly predictive of follow-up LVEF were deceleration time (r = 0.69, p = 0.0006), wall motion score index (WMSI) (r = -0.63, p = 0.002), LV mass (r = 0.56, p = 0.008) and LVEF on dobutamine (r = 0.84, p = 0.0001). When either deceleration time or WMSI or LV mass was entered into a regression equation to predict follow-up LVEF, the LVEF on dobutamine added significantly to predictive power. However, if LVEF on dobutamine was entered first, none of the other three variables added significantly to prediction. Baseline LV sphericity at end diastole (ED) (r = 0.13, p = 0.6) did not correlate with follow-up LV sphericity in ED, whereas LV sphericity in ED on dobutamine (ED [r = 0.70, p = 0.0004]) correlated with LV sphericity in ED on follow up.

CONCLUSIONS

This study demonstrates that dobutamine-induced improvement in baseline LVEF and LV sphericity identifies patients with IDC who exhibit substantial improvement in LV function and geometry over time.

Cardiovascular responses to exercise in children and adolescents with myocardial dysfunction

OBJECTIVES

The objective of this study was to understand the expected hemodynamic responses to exercise in children and adolescents with myocardial dysfunction.

METHODS AND RESULTS

With the use of Doppler and M-mode echocardiography, cardiovascular changes during maximal semisupine exercise in 11 patients (7 to 17 years old) with myocardial dysfunction were compared with those of a healthy control group (n = 11). Endurance fitness and mean values for maximal cardiac index, stroke index, heart rate, peak aortic velocity, and left ventricular shortening fraction were all significantly lower in the patients (P <.05). Stroke volume rose at the onset of exercise in both groups; whereas values were subsequently stable in the control subjects, stroke volume declined at high-intensity exercise in the patients.

CONCLUSIONS

These findings imply that augmented myocardial contractility is necessary to sustain stroke volume during exercise. Moreover, the results suggest that pattern of stroke volume response to exercise may serve as a useful marker of myocardial function in children with heart disease.

Redistribution in thallium-201 myocardial imaging soon after successful coronary stenting--tomographic evaluation during coronary hyperemia induced by adenosine

To evaluate the clinical significance of reversible perfusion defects that were observed soon after the successful deployment of a coronary stent, 47 patients underwent thallium-201 myocardial scintigraphy and radionuclide angiography in conjunction with adenosine-induced coronary hyperemia before and after complete revascularization. Coronary angiography showed a significant decrease in the percent diameter stenosis (from 87+/-11% before stenting to -1+/-5% after stenting, p<0.01) with no major dissection, residual stenosis, or intra-stent formation of thrombus. Even after the angiographically successful procedure, reversible perfusion defects were present in 17 (36%) of the 47 patients, none of whom showed any wall motion abnormalities during the infusion of adenosine. Disease duration was significantly longer and collateral vessels were more common in the patients with than in those without thallium redistribution, whereas the other clinical, pre- and post-stent angiographic and hemodynamic factors were similar. In conclusion, reversible perfusion defects without wall motion abnormalities were demonstrated during the infusion of adenosine in approximately one-third of patients soon after coronary stenting, and were not consistently related to acute unfavorable outcomes of stent placement.