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New Echocardiographic Insights in Short QT Syndrome More Than a Channelopathy?

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New Echocardiographic Insights in Short QT Syndrome More Than a Channelopathy? New echocardiographic insights in short QT syndrome: More than a channelopathy? Simone Frea, MD,* Carla Giustetto, MD,* Michele Capriolo, MD,* Chiara Scrocco, MD,* Cristina Fornengo, MD,* Sara Benedetto, MD,* Francesca Bianchi, MD,† Stefano Pidello, MD,* Mara Morello, MD,* Fiorenzo Gaita, MD* From the *Division of Cardiology, University of Turin, Department of Medical Sciences, Città della Salute e della Scienza Hospital, Turin, Italy, and †Division of Cardiology, Mauriziano Hospital, Turin, Italy. BACKGROUND Short QT syndrome (SQTS) is a congenital ion SQTS group than in controls; each parameter showed a significant channel disease characterized by an increased risk of sudden inverse correlation with QT interval but not with QT dispersion. cardiac death. Little is known about the possibility that accelerated repolarization alters mechanical function in SQTS. CONCLUSION This study showed that in SQTS systolic function may also be affected. SQTS patients presented a significant OBJECTIVES The study investigated the presence of left ventric- dispersion of myocardial contraction. TDI and STE could become ular dysfunction and mechanical dispersion, assessed by tissue part of the evaluation of this rare disease. Doppler imaging (TDI) and speckle tracking echocardiography (STE), and their correlation with QT interval duration and genetics. KEYWORDS Short QT syndrome; Genetics; Arrhythmias; Tissue Doppler imaging; Speckle tracking echocardiography; Global METHODS Fifteen SQTS patients (7 with HERG and 3 with KCNQ1 longitudinal strain mutation) were studied. Electrocardiographic and echocardio- graphic parameters were compared with age- and sex-matched ABBREVIATIONS CD ¼ contraction duration; ECG ¼ electro- healthy controls. cardiography; GCS ¼ global circumferential strain; GLS ¼ global longitudinal strain; HQ ¼ hydroquinidine; ICD ¼ implantable RESULTS When compared to the control group, SQTS patients cardioverter defibrillator; LV ¼ left ventricular; MPI ¼ myocardial showed reduced left ventricular contraction (global longitudinal performance index; SD ¼ standard deviation; SQTS ¼ short QT À Ϯ À Ϯ P o strain: 16.0% 3.4% vs 22.6% 1.7%, .001; myocardial syndrome; STE ¼ speckle tracking echocardiography; TDI ¼ tissue Ϯ Ϯ P o performance index 0.59 0.17 vs 0.34 0.08, .001) and a Doppler imaging higher incidence of ejection fraction o55% (odds ratio 11, 95% confidence interval 1.045–374, P ¼ .04). Mechanical dispersion (Heart Rhythm 2015;12:2096–2105) I 2015 Heart Rhythm Society. assessed by TDI (P o .01) and STE (P o .001) was higher in the All rights reserved. Introduction dispersed myocardial contraction,7,8 which have been asso- Short QT syndrome (SQTS) is a primary cardiac electrical ciated with a higher risk of cardiac arrhythmias. disease caused by autosomal dominant gain-of-function In the setting of SQTS a different density of slow delayed fi mutations in genes encoding for potassium channels, resulting recti er potassium current (IKs) and inwardly rectifying in a substantial shortening of QT interval,1–4 which predis- potassium current (IKr) channels was shown in the ven- poses to life-threatening arrhythmias. Left ventricular (LV) tricles. This could lead to a heterogeneous shortening of the function has been assumed to be normal in SQTS patients and action potential duration through different segments of the echocardiography has traditionally been performed only to left ventricle and could be the substrate for ventricular exclude an additional heart disease. There are clues in support arrhythmias in SQTS patients. Little is known about the of the hypothesis that electrical changes may cause subtle possibility that accelerated repolarization resulting in a mechanical dysfunction, as previously reported in long QT shorter action potential could alter the mechanical function syndrome patients.5,6 Moreover, recent strain studies revealed in SQTS. A previous study that evaluated SQTS patients by fi that patients with long QT syndrome have both prolonged and conventional echocardiography did not show any signi cant alteration in LV function.9 Tissue Doppler imaging (TDI) and speckle tracking echocardiography (STE) have been Address reprint requests and correspondence: proven to be superior for assessment of global and regional Dr Stefano Pidello, 10 Division of Cardiology, University of Turin and A.O. Città della Salute e LV function. We hypothesized that contraction duration della Scienza, Turin, Italy. E-mail address: [email protected]. (CD) is inhomogeneously distributed through the left 1547-5271/$-see front matter B 2015 Heart Rhythm Society. All rights reserved. http://dx.doi.org/10.1016/j.hrthm.2015.05.024 Frea et al Echocardiography in Short QT Syndrome Table 1 Clinical and electrocardiographic characteristics of short QT syndrome patients Basal ECG Therapy Clinical features Patient Involved QT interval QTc interval QTc interval on HQ Daily HQ dosage Implanted Family history First clinical Events at Family no. Sex Age gene HR (ms) (ms) (ms) (mg) device of SD manifestation follow-up A 1 M 44 KCNH2 66 270 280 390* 1000 ICD Y Syncope, AF – 2 F 41 KCNH2 78 260 300* 430 500 ICD Y – AF B 3 F 49 KCNH2 88 250 300* 340 500 ICD Y Palpitations – 4 M 19 KCNH2 77 300 340 370* 900 – Y –– C 5 F 58 Unknown 68 300 320* 380 500 ICD Y – NSVT 6 M 31 Unknown 67 310 330* 400 500 ICD Y – NSVT D 7 M 18 KCNH2 66 260 270 310* 1000 ILR Y –– 8 F 23 KCNH2 65 300 310 400* 750 ILR Y – NSVT 9 F 48 KCNH2 77 300 340 420* 750 ICD Y aSD NSVT E 10 M 36 KCNQ1 70 320 340* 360 450 ––Palpitations – 11 M 5 KCNQ1 95 280 350* –––––– 12 F 10 KCNQ1 68 320 340* –––––– F 13 M 22 Unknown 80 310 350* ––ILR Y Syncope – G 14 M 22 Unknown 70 315 340* 390 600 ILR – Palpitations – H 15 M 27 Unknown 62 320 325* ––ILR Y Syncope – AF ¼ atrial fibrillation; aSD ¼ aborted sudden death; HQ ¼ hydroquinidine; ICD ¼ implantable cardioverter-defibrillator; ILR ¼ implantable loop recorder; nsVT ¼ nonsustained ventricular tachycardia; Y ¼ yes. *QTc value at the time of echocardiogram index. atrial due to frequent nonsustainedtreatment ventricular for tachycardia, primary or prevention for ofpalpitations. ventricular Eleven arrhythmias, patients receivedparoxysmal hydroquinidine atrial (HQ) documented with thesyncope, ICD 4 patients or had loop-recorder, nonsustainedcardiac ventricular 1 tachycardia patient arrest, had implantable 3 loop-recorder. patientsan One implantable had patient cardioverterknown a had mutation de was a probably foundpatients in had previous arrhythmic 5 a patients.mutation mutation Six in in patients KCNQ1 KCNH2 had patients (SQTS2), (HERG) underwent genetic whereas was analysis for no found SQTS:the in study (SQTS1) 7 ( patients and a 3 the shortest QTcdeviation intervals (SD) and in as the any difference of between the the longest and 12 ECG leads. Fifteen patients with diagnosisShort of QT SQTS syndrome patients Methods cologic therapy. dispersion is related to genotypesought and to is affected evaluate byventricle, whether pharma- leading to echocardiographic mechanical dispersion. mechanical Furthermore, we tion with standard echocardiography,we TDI, and performed STE. ato comprehensive echocardiographic evaluate evalua- systolic and diastolicdiscontinue treatment impairment before echocardiographic inEindhoven, evaluation. NL). SQTS, SQTSAdvanced patients Quanti on(Philips) chronic and analyzed HQ with the didThe software echocardiographic not CMQ studies 9 were forEchocardiographic QLAB performed studies using iE33 In SQTS patients on HQ therapy ECG Patient 2 in echocardiographic examination. A 12-lead ECG wasElectrocardiography obtained in all subjects at the time of informed consent. institutional review board; patients andthe controls gave Declaration written of Helsinki and was approvedechocardiography. by the local QT interval correctednormal for clinical heart examination,from rate hospital electrocardiography (QTc), and staff, (ECG), Fifteen healthy standard served age- and asControl sex-matched group a individuals, recruited control group. All had compared to ECG obtained before treatment. correction. Since this is, to the best of our knowledge, the The present study conforms with the principles outlined in fi brillation prophylaxis ( Table 1 12 QTc dispersion was measured as the standard Table 1 ). None had structural heart disease. All 15 fi fi cation Software version 9.0 (Philips, brillation, and 3 had nondocumented . Bazett ’ Table 1 s formula was used for QT fi Figure 1 brillator (ICD) and 5 an ). 11 shows the ECG of were included in fi ndings were fi rst study 2097 13 2098 Heart Rhythm, Vol 12, No 10, October 2015 Figure 1 Electrocardiogram of Patient 2 in Table 1 at time of diagnosis. Heart rate 78 bpm, QT 260 ms, QT interval corrected for heart rate 300 ms. Frea et al Echocardiography in Short QT Syndrome 2099 Standard echocardiography to end of S3 (zero-crossing) if S3 was present, and to the The following parameters were assessed: LV dimensions, peak of contraction detected with tissue color M-mode; systolic (ejection fraction, peak lateral S2 velocity, and and SD of these values, calculated as a parameter of myocardial performance index [MPI]) and diastolic function mechanical dispersion of contraction. (E/A ratio, deceleration time, isovolumic contraction and relaxation times, septal and lateral e0 and a0, E/e0 ratio), atrial Speckle tracking echocardiography dimensions, right ventricular dimensions, and function. Prede- We assessed longitudinal and circumferential strains by the fined parameters of systolic dysfunction were as follows: 14 speckle tracking technique with a frame rate 4 70 frames EF o 55%, peak lateral S2 velocity o 8cm/s, and MPI 15 per second. Three cardiac cycles were analyzed. We assessed 4 0.47. Predefined parameters of diastolic dysfunction were 0 0 the following parameters from myocardial strain: as follows: septal e o 8 cm/s, lateral e o 10 cm/s, left atrial volume Z 34 mL/m2.16 (1) Global longitudinal strain (GLS), calculated as the Moreover, the interval from the end of the T wave to average of longitudinal maximum myocardial shortening aortic valve closure and the interval from the beginning of from 17 LV segments. A GLS value o À18.9% was the Q wave to closure of the aortic valve were analyzed.
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