| Part 1 Feasibility Study of Quantitative Evaluation of Left Atrial Function by Cardiac Magnetic Resonance Feature TrackingObjective To explore the feasibility of quantitative evaluation of left atrial function by cardiac magnetic resonance feature tracking(CMR-FT).Methods Healthy individuals with normal magnetic resonance examination results were enrolled according to the inclusion criteria.Cardiac long-and short-axis images and cine were obtained using semi-Fourier single-shot technique and balanced steady-state free precession sequence.The following LA global functional parameters were quantitively analyzed: reservoir function(total ejection fraction [LA total EF],total strain [?s],peak positive strain rate[SRs]),conduit function(passive ejection fraction [LA passive EF],passive strain [?e],peak early-negative SR [SRe]),and booster pump function(active ejection fraction [LA active EF],active strain [?a],peak late-negative SR [SRa]).Results A total of 63 volunteers were included in this study.Of 63 volunteers,34 were males and 29 females;and 19 volunteers were aged ? 29 years,23 were aged 30-44 years and 21 were aged ? 45 years.The anteroposterior diameter of left atrium was 26.1 ± 4.5 mm,and the transverse diameter was 54.8 ± 5.9 mm.The total ejection fraction of left atrium was 63.5 ±6.9 %,total strain was 45.9 ± 11.7%,and total strain rate was 1.5 ± 0.5 s-1.The passive ejection fraction of left atrium was 24.6 ± 9.1,passive strain was 22.2 ±8.1 %,and passive strain rate was-0.8 ± 0.3)s-1.The active ejection fraction of left atrium was 51.3 ± 8.9 %,active strain was 23.7 ± 9.2 %,and active strain rate was-1.3 ± 0.5 s-1.There were significant differences in the body surface area,the left atrial diameters,maximal volume and pre-contracted volume between the males and the females(all P < 0.05),while the differences in the other left atrial function parameters were not significant(all P > 0.05).There were significant differences in the left atrial conduit function among the different age groups(all P < 0.05),while there were no significant differences in reservoir or booster pump function parameters.Intraclass correlation coefficient and Bland-Altman analysis showed better consistency between the intra-and inter-observersConclusion CMR-FT can be used as a noninvasive method for the comprehensive assessment of left atrial function due to its good repeatability.Part 2 Quantification of Left Atrial Function in Patients with Non-obstructive Hypertrophic Cardiomyopathy by Cardiovascular Magnetic Resonance Feature Tracking ImagingObjective To evaluate the LA function in patients with non-obstructive HCM(NOHCM)utilizing cardiovascular magnetic resonance feature tracking(CMR-FT)Methods Thirty-three patients with NOHCM and 28 healthy controls were studied.The global and regional LA function and left ventricular(LV)function were compared between the two groups.The following LA global functional parameters were quantitively analyzed: reservoir function(total ejection fraction[LA total EF],total strain [?s],peak positive strain rate [SRs]),conduit function(passive ejection fraction [LA passive EF],passive strain [?e],peak early-negative SR [SRe]),and booster pump function(active ejection fraction[LA active EF],active strain [?a],peak late-negative SR [SRa]).The LA wall was automatically divided into 6 segments: anterior,antero-roof,inferior,septal,septal-roof and lateral.Three LA strain parameters(?s,?e,?a)and their corresponding strain rate parameters(SRs,SRe,SRa)during the reservoir,conduit and booster pump LA phases were segmentally measured and analyzed.Results The LA reservoir(LA total EF: 57.6±8.2% vs.63.9±6.4%,P<0.01;?s: 35.0±12.0% vs.41.5±11.2%,P=0.03;SRs: 1.3 ± 0.4 s-1 vs.1.5 ± 0.4 s-1,P=0.02)and conduit function(LA passive EF: 28.7±9.1% vs.37.1±10.0%,P<0.01;?e: 18.7±7.9% vs.25.9±10.0%,P<0.01;SRe:-0.8±0.3 s-1 vs.-1.1±0.4s-1,P<0.01)were all impaired in patients with NOHCM when compared with healthy controls,while LA booster pump function was preserved.The LA segmental strain and strain rate analysis demonstrated that the three functions of inferior,booster pump function of antero-roof,reservoir and conduit function of septal,conduit function of antero-roof(all P<0.05)were all decreased in the NOHCM cohort.Correlations between LA functional parameters and LV conventional function and LA functional parameters and baseline parameters (age,body surface area and NYHA classification)were weak.The two strongest relations were between ?s and LA total EF(r = 0.84,P < 0.01),?a and LA active EF(r = 0.83,P < 0.01).Conclusions Compared with healthy controls,patients with NOHCM have LA reservoir and conduit dysfunction,and regional LA deformation before LA enlargement.CMR-FT identifies LA dysfunction and deformation at an early stage.Part 3 Characteristics and Prognostic Value of Left Atrial Strain in Hypertrophic Cardiomyopathy with Normal Atrium Size: A Cardiovascular Magnetic Resonance Feature Tracking studyObjective To evaluate the LA global and regional function using CMR-FT in HCM patients and to assess the prognostic value of LA deformation.Methods Sixty-one participants with normal LA size among 574 patients with HCM who underwent CMR screening were retrospectively analyzed.LA reservoir,conduit,and contractile function were respectively quantified by volumetric and CMR-FT derived strain and strain rate parameters from 2-and4-chamber cine imaging.The relationships of LA function to clinical endpoints(all-cause death,new-onset or worsening heart failure(HF),and paroxysmal or persistent atrial fibrillation)were evaluated by using Cox models and the area under the receiver operating characteristic curve.Results Compared to controls,HCM patients had impaired LA reservoir function(total strain [%]: HCM 34.5±12.1,Controls 41.1 ± 10.7,p<0.01;total SR [s-1]: HCM 1.2 ± 0.4,Controls 1.4±0.4,p=0.01)and conduit function(passive strain [%]: HCM 17.6±7.8,Controls 24.9±8.9,p<0.01;passive SR [s-1]:HCM-0.7±0.4,Controls-1.0±0.4,p<0.01).HCM patients who developed the clinical endpoint had lower LA reservoir strain/strain rate,larger LA mass index and LV maximal wall thickness without differences in LA volumetric parameters.LA global reservoir functional parameters were associated with adverse outcomes independently of LVEF.Conclusions LA strain may become a novel prognostic factor of HCM and evaluate the severity for HCM patients.CMR-FT is suggested to implement in the routine and early evaluation of HCM patients. |
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