LiNa Wu

Prediction of long-term outcome of cardiac resynchronization therapy by acute pressure-volume loop measurements.

Invasive assessment of acute haemodynamic response to biventricular pacing has been proposed as a tool to determine individual response and to optimize the effects of CRT. However, the long‐term results of this approach have been poorly studied. The present study relates acute haemodynamic effects of CRT to long‐term outcome.

Scar tissue–guided left ventricular lead placement for cardiac resynchronization therapy in patients with ischemic cardiomyopathy: An acute pressure-volume loop study

BACKGROUND Response to cardiac resynchronization therapy (CRT) is hampered by the extent and location of left ventricular (LV) scar tissue. It is commonly advised to avoid scar tissue while placing the LV lead. However, whether individual patients benefit from this strategy remains unclear. METHODS Thirty-two CRT candidates with ischemic cardiomyopathy were enrolled from 2 successive clinical trials (TBS and E-pot study). Magnetic resonance imaging with late contrast enhancement was performed to assess location, degree and transmurality of LV scar tissue. Patients underwent invasive pressure-volume loop measurements to assess acute LV pump function changes during pacing at posterolateral (PL) and anterolateral LV sites. RESULTS In the study population (26 [81%] men, ejection fraction [EF] 22% ± 8%, QRS 149 ± 20 milliseconds), baseline mean stroke work (SW) and dP/dtmax were 4.4 ± 2.2 L∙mmHg and 849 ± 212 mmHg/s, respectively. The extent of scar tissue was inversely related to the acute increase in SW during pacing (R = -0.53, P = .002). Stimulating PL scar tissue resulted in deterioration of pump function (∆SW -17% ± 17%, P = .018), whereas pacing PL viable tissue led to an increase in pump function (∆SW +62% ± 51%, P < .001). Switching from pacing at the location of scar tissue, irrespective of the scar location, to viable tissue showed a significant increase in SW (-8% ± 20% vs +20 ± 40, P = .004). CONCLUSIONS The extent of LV scar tissue is inversely related to acute pump function improvement during CRT. Pacing at the location of (transmural) scar tissue at any site of the LV will generally deteriorate LV pump function. Placing the LV lead over viable myocardium significantly improves pump function as compared with pacing at the location of scar tissue in patients with ischemic cardiomyopathy.

Impaired Hyperemic Myocardial Blood Flow Is Associated With Inducibility of Ventricular Arrhythmia in Ischemic Cardiomyopathy

Background—Risk stratification for ventricular arrhythmias (VAs) is important to refine selection criteria for primary prevention implantable cardioverter defibrillator therapy. Impaired hyperemic myocardial blood flow (MBF) is associated with increased mortality rate in ischemic and nonischemic cardiomyopathy, which may be attributed to electric instability inducing VAs. The aim of this pilot study was to assess whether hyperemic MBF impairment may be related with VA inducibility in patients with ischemic cardiomyopathy. Methods and Results—Thirty patients with ischemic cardiomyopathy referred for primary prevention implantable cardioverter defibrillator implantation were prospectively included (26 men; 65±8 years old; left ventricular ejection fraction, 29±6%). [15O]H2O positron-emission tomography was performed to quantify resting MBF, hyperemic MBF, and coronary flow reserve. Left ventricular dimensions, function, and scar burden were assessed with cardiovascular magnetic resonance imaging. An electrophysiological study was performed to test VA inducibility. Positive electrophysiological study patients (n=12) showed reduced hyperemic MBF (1.25±0.30 versus 1.66±0.38 mL·min−1·g−1; P<0.01) and coronary flow reserve (1.59±0.49 versus 2.12±0.48; P<0.01) compared with electrophysiological study negative patients (n=18). In electrophysiological study positive patients, the number of scar segments >75% transmurality was higher (P<0.05), although scar size and border zone did not differ. Receiver-operating characteristic curve analysis indicated that impaired hyperemic MBF (area under the curve, 0.84; 95% confidence intervals [0.69–0.99]) and coronary flow reserve (area under the curve, 0.77; 95% confidence intervals [0.57–0.96]) were associated with VA inducibility. Conclusions—In this pilot study, impaired hyperemic MBF and coronary flow reserve were associated with VA inducibility in patients with ischemic cardiomyopathy. These results are hypothesis generating for a potential role of quantitative positron-emission tomography perfusion imaging in risk stratification for VAs.

Prediction of Acute Response to Cardiac Resynchronization Therapy by Means of the Misbalance in Regional Left Ventricular Myocardial Work

BACKGROUND Patients with left ventricular (LV) dyssynchrony have a marked misbalance in LV myocardial work distribution, with wasted work in the septum and increased work in the lateral wall. We hypothesized that a low septum-to-lateral wall (SL) myocardial work ratio at baseline predicts acute LV pump function improvement during cardiac resynchronization therapy (CRT). METHODS AND RESULTS Twenty patients (age 65 ± 10 y, 15 men) underwent cardiac magnetic resonance (CMR) tagging for regional LV circumferential strain assessment and invasive pressure-volume loop assessment at baseline and during biventricular pacing. Segmental work at baseline was calculated from regional strain rate and LV pressure. Subsequently, the SL work ratio was calculated and related to acute pump function (stroke work [SW]) improvement during CRT. During biventricular pacing, SW increased by 33% (P <.001). SL work ratio at baseline was found to be significantly related to SW improvement by means of CRT (R = -0.54; P = .015). Moreover, it proved to be the only marker that was significantly related to acute response to CRT, whereas QRS duration and other measures of dyssynchrony or dyscoordination were not. CONCLUSIONS The contribution of the septum to LV work varies widely in CRT candidates with left bundle branch block. The lower the septal contribution to myocardial work at baseline, the higher the acute pump function improvement that can be achieved during CRT.

Bifocal left ventricular stimulation or the optimal left ventricular stimulation site in cardiac resynchronization therapy: a pressure–volume loop study

AIMS Several implantation strategies have been proposed to improve response to cardiac resynchronization therapy (CRT), including bifocal left ventricular (LV) stimulation and optimal single-LV lead placement. This study aimed to compare these two strategies during invasive pressure-volume (PV) loop measurements. METHODS AND RESULTS Thirty-three patients eligible for CRT were included [21 (64%) men, 20 (61%) ischaemic aetiology, QRS 155 ± 23 ms], and underwent cardiac magnetic resonance (CMR) imaging and invasive PV loop measurements. Left ventricular pump function was characterized by stroke work (SW) and dP/dtmax (5.1 ± 3.4 L mmHg and 856 ± 190 mmHg/s, respectively). Haemodynamic response was assessed during stimulation at single-LV sites and during bifocal LV [anterolateral and posterolateral (PL)] stimulation. Response during bifocal LV stimulation was not significantly higher compared with standard PL pacing (SW; β = 9.4 ± 5.4, P = 0.080; dP/dtmax, β = 0.2 ± 1.9, P = 0.922). However, mean pump function improvement was significantly higher during stimulation at the optimal LV site compared with bifocal LV stimulation (SW; β = 12.7 ± 5.1, P = 0.012; dP/dtmax, β = 3.3 ± 1.2, P = 0.020). Myocardial tissue properties were assessed by CMR tissue tagging. Mechanical activation at the optimal LV site was significantly more delayed compared with the worst LV site (431 ± 93 ms vs. 326 ± 127 ms; P = 0.004). CONCLUSION Stimulation at the optimal LV site showed a significantly higher pump function improvement compared with bifocal LV stimulation. Mechanical activation at the optimal LV site was significantly more delayed compared with the non-optimal LV site. In general, these results suggest that implantation of a second LV lead yields no additional benefit over implantation of one optimally placed LV lead. However, a bifocal approach might be beneficial in the individual patient.

Strain analysis in CRT candidates using the novel segment length in cine (SLICE) post-processing technique on standard CMR cine images

ObjectivesAlthough myocardial strain analysis is a potential tool to improve patient selection for cardiac resynchronization therapy (CRT), there is currently no validated clinical approach to derive segmental strains. We evaluated the novel segment length in cine (SLICE) technique to derive segmental strains from standard cardiovascular MR (CMR) cine images in CRT candidates.MethodsTwenty-seven patients with left bundle branch block underwent CMR examination including cine imaging and myocardial tagging (CMR-TAG). SLICE was performed by measuring segment length between anatomical landmarks throughout all phases on short-axis cines. This measure of frame-to-frame segment length change was compared to CMR-TAG circumferential strain measurements. Subsequently, conventional markers of CRT response were calculated.ResultsSegmental strains showed good to excellent agreement between SLICE and CMR-TAG (septum strain, intraclass correlation coefficient (ICC) 0.76; lateral wall strain, ICC 0.66). Conventional markers of CRT response also showed close agreement between both methods (ICC 0.61–0.78). Reproducibility of SLICE was excellent for intra-observer testing (all ICC ≥0.76) and good for interobserver testing (all ICC ≥0.61).ConclusionsThe novel SLICE post-processing technique on standard CMR cine images offers both accurate and robust segmental strain measures compared to the ‘gold standard’ CMR-TAG technique, and has the advantage of being widely available.Key Points• Myocardial strain analysis could potentially improve patient selection for CRT.• Currently a well validated clinical approach to derive segmental strains is lacking.• The novel SLICE technique derives segmental strains from standard CMR cine images.• SLICE-derived strain markers of CRT response showed close agreement with CMR-TAG.• Future studies will focus on the prognostic value of SLICE in CRT candidates.

SYMPATHETIC DENERVATION IS ASSOCIATED WITH MICROVASCULAR DYSFUNCTION IN NON-INFARCTED MYOCARDIUM IN PATIENTS WITH CARDIOMYOPATHY

Sympathetic denervation typically occurs in the infarcted myocardium and is associated with sudden cardiac death. Impaired innervation was also demonstrated in non-infarcted myocardium in ischaemic and dilated cardiomyopathy (ICMPandDCMP). Factors affecting sympatheticnerveintegrity inremotemyocardium areunknown. Perfusionabnor- malities,evenintheabsenceofepicardialcoronaryarterydisease,mayrelatetosympatheticdysfunction.Thisstudywas aimed to assess the interrelations of myocardial blood flow (MBF), contractile function, and sympathetic innervation in non-infarcted remote myocardium. Seventy patients with ICMP or DCMP and LVEF ≤35% were included. ( 15 O)H2O- and ( 11 C)hydroxyephedrine (HED)PETwasperformedtoquantify restingMBF,hyperaemicMBF,andsympatheticinnervation.Cardiovascularmag- neticresonance(CMR)imagingwasperformedtoassessleftventricularfunction,mass,wallthickening,andscarsize.Wall thickening, ( 11 C)HED retention index (RI), and MBF wereassessed in remote segments without scar, selected on CMR. ( 11 C)HEDRIwascorrelatedwithrestingMBF(r ¼ 0.41,P , 0.001)andhyperaemicMBF(r ¼ 0.55,P , 0.001)inremote myocardiuminbothICMPandDCMP.Inaddition,LVvolumes(r ¼ 20.40,P ¼ 0.001),LVmass(r ¼ 20.31,P ¼ 0.008), andwallthickening(r ¼ 0.45,P , 0.001)correlatedwithremote( 11 C)HEDRI.Multivariableanalysisrevealedthathyper- aemic MBF (B ¼ 0.79, P , 0.001), wall thickening (B ¼ 0.01, P ¼ 0.03), and LVEDV (B ¼ 20.03, P ¼ 0.02) were inde- pendent predictors for remote ( 11 C)HED RI. Conclusion Hyperaemic MBF is independently associated with sympathetic innervation in non-infarcted remote myocardium in patients with ICMP and DCMP. This suggests that microvascular dysfunction might be an important factor related to sympathetic nerve integrity. Whether impaired hyperaemic MBF is the primary cause of this relation remains unclear.

IMPAIRED HYPEREMIC MYOCARDIAL BLOOD FLOW IS ASSOCIATED WITH INDUCIBILITY OF VENTRICULAR ARRHYTHMIA IN ISCHEMIC CARDIOMYOPATHY

Risk stratification for ventricular arrhythmias (VA) is important to refine selection criteria for primary prevention implantable cardioverter-defibrillator therapy. Impaired hyperemic myocardial blood flow (MBF) is associated with increased mortality rate in ischemic and non-ischemic cardiomyopathy

ELECTRICAL RESYNCHRONIZATION IS NOT RELATED TO HEMODYNAMIC RESPONSE IN CARDIAC RESYNCHRONIZATION THERAPY

Cardiac resynchronization therapy (CRT) is based on restoring left ventricular dyssynchrony. It is known that CRT induced changes in QRS duration poorly predict hemodynamic effect. This study assessed invasively obtained endocardial and epicardial left ventricular activation with and without CRT and

THE INFLUENCE OF RIGHT VENTRICULAR PACING ON RESPONSE TO BIVENTRICULAR PACING: AN ACUTE PRESSURE-VOLUME LOOP STUDY

Background: Cardiac resynchronization therapy (CRT) is an established therapy for end-stage heart failure. It is currently recommended to position the left ventricular (LV) lead at the postero-lateral (PL) wall. However, the position of the right ventricular (RV) lead remains controversial, since it may be associated with adverse hemodynamic effects. This may partly explain non-response to CRT. We hypothesized that RV pacing during biventricular pacing signiicantly modulates response. We studied the acute invasive hemodynamic response of RV, LV and biventricular pacing.