Evaluation of QT interval duration and dispersion and proposed clinical criteria in diagnosis of long QT syndrome in patients with a genetically uniform type of LQT1

Swan, Heikki; Saarinen, Kirsi; Kontula, Kimmo; Toivonen, Lauri; Viitasalo, Matti

doi:10.1016/s0735-1097(98)00248-4

Cited by 56 publications

(29 citation statements)

References 23 publications

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“…Follow-up testing demonstrated normal left ventricular function (left ventricular ejection fraction Ն50%) and normal coronary arteries. Patients were excluded if they had a resting corrected QT interval (QTc) Ͼ460 ms (for men) or a QTc Ͼ480 ms (for women) 20,21 or if a reversible cause of cardiac arrest such as marked hypokalemia or drug overdose was present. Investigators and coordinators performed a consultation/assessment whenever possible to determine whether reversible causes, including drug overdose or a proarrhythmic effect, were present, or they reviewed the medical record when the arrest was no longer acute.…”

Section: Patientsmentioning

confidence: 99%

Systematic Assessment of Patients With Unexplained Cardiac Arrest

et al. 2009

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Background-Cardiac arrest without evident cardiac disease may be caused by subclinical genetic conditions. Provocative testing to unmask a phenotype is often necessary to detect primary electrical disease, direct genetic testing, and perform family screening. Methods and Results-Patients with apparently unexplained cardiac arrest and no evident cardiac disease (normal cardiac function on echocardiogram, no evidence of coronary artery disease, and a normal ECG) underwent systematic evaluation that included cardiac magnetic resonance imaging, signal-averaged ECG, exercise testing, drug challenge, and selective electrophysiological testing. Diagnostic criteria were based on accepted criteria or provocation of the characteristic clinical features for long-QT syndrome, catecholaminergic polymorphic ventricular tachycardia, Brugada syndrome, early repolarization, arrhythmogenic right ventricular cardiomyopathy, coronary spasm, and myocarditis. Sixty-three patients in 9 centers were enrolled (age 43.0Ϯ13.4 years, 29 women Key Words: heart arrest Ⅲ diagnosis Ⅲ catecholamines Ⅲ genetics Ⅲ magnetic resonance imaging C ardiac arrest in the absence of evident structural heart disease is uncommon, with a broad differential diagnosis that includes subclinical cardiomyopathy, primary electrical disorders, and idiopathic ventricular fibrillation. [1][2][3][4][5] Growing recognition of the clinical features of uncommon genetic conditions that lead to cardiac arrest has reduced the number of cases that remain unexplained. Clinical Perspective on p 285Cardiac ion channel disorders that result in "primary electrical disease" may be difficult to diagnose unless overt ECG abnormalities are present. 6 -12 Subclinical QT prolongation, ST-segment shifts, or ventricular arrhythmias may be electrocardiographically subtle or intermittent. [13][14][15][16][17][18] Although an implantable cardioverter defibrillator (ICD) is indicated in patients who have had a cardiac arrest without a correctable cause, 19 optimal management to reduce recurrence requires a diagnosis. In addition, screening of family members is dependent on recognition of a phenotype that allows case finding, targeted genetic testing, and prophylactic intervention. We describe the yield of sequential noninvasive and invasive testing in Patients were enrolled between January 1, 2004, and October 1, 2008, in 8 adult and 1 pediatric electrophysiology center across Canada. During the recruitment period, the 9 involved centers enrolled 63 patients, during which time they implanted 1877 secondary-prevention ICDs (3.4%). On the basis of projections from the systematic data from a single year, an estimated 105 patients (5.6%) would have been excluded from enrollment because of cardiac arrest manifestly attributed to long-QT syndrome (LQTS), Brugada syndrome. and arrhythmogenic right ventricular cardiomyopathy (ARVC). 23 All patients provided written informed consent. The protocol was approved by the Health Sciences Research Ethics Board of the University of Western Ontario, as well...

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Section: Patientsmentioning

confidence: 99%

Systematic Assessment of Patients With Unexplained Cardiac Arrest

et al. 2009

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“…These 2 facts appear difficult to reconcile with one another, although it is known that penetrance (ie, the number of individuals having a particular genotype relative to those displaying the associated clinical phenotype) is rather low 31,32 in families with documented LQT1 mutations, histories of seizures, and sudden cardiac death. A far too simplistic explanation would be that individuals with mutated I Ks channel proteins and elevated sympathetic tone lack the ability to compensate and limit excessive APD lengthening as a result of other causes such as extreme bradycardia, hypothyroidism, hypokalemia, changes in autonomic neural influences, or exposure to drugs affecting other repolarizing currents (eg, I Na,slow , I Cl , I to , I Kr , I K1 ).…”

Section: Discussionmentioning

confidence: 99%

Restricting Excessive Cardiac Action Potential and QT Prolongation

et al. 2005

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Background-Although pharmacological block of the slow, delayed rectifier potassium current (I Ks ) by chromanol 293B, L-735,821, or HMR-1556 produces little effect on action potential duration (APD) in isolated rabbit and dog ventricular myocytes, the effect of I Ks block on normal human ventricular muscle APD is not known. Therefore, studies were conducted to elucidate the role of I Ks in normal human ventricular muscle and in preparations in which both repolarization reserve was attenuated and sympathetic activation was increased by exogenous dofetilide and adrenaline. Methods and Results-Preparations were obtained from undiseased organ donors. Action potentials were measured in ventricular trabeculae and papillary muscles using conventional microelectrode techniques; membrane currents were measured in ventricular myocytes using voltage-clamp techniques. Chromanol 293B (10 mol/L), L-735,821 (100 nmol/L), and HMR-1556 (100 nmol/L and 1 mol/L) produced a Ͻ12-ms change in APD while pacing at cycle lengths ranging from 300 to 5000 ms, whereas the I Kr blockers sotalol and E-4031 markedly lengthened APD.

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“…Follow-up testing demonstrated normal left ventricular function (left ventricular ejection fraction Ն50%) and normal coronary arteries. Patients were excluded when males had a resting corrected QT (QTc) Ͼ460 ms and females with a QTc Ͼ480 ms 22,23 or when a reversible cause of cardiac arrest, such as marked hypokalemia or drug overdose, was present. No patient or family member had a QTc Ͻ350 ms.…”

Section: Patientsmentioning

confidence: 99%

Diagnosis of Unexplained Cardiac Arrest

et al. 2005

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Background— Cardiac arrest with preserved left ventricular function may be caused by uncommon genetic conditions. Although these may be evident on the ECG, long-term monitoring or provocative testing is often necessary to unmask latent primary electrical disease. Methods and Results— Patients with unexplained cardiac arrest and no evident cardiac disease (normal left ventricular function, coronary arteries, and resting corrected QT) underwent pharmacological challenge with adrenaline and procainamide infusions to unmask subclinical primary electrical disease. Family members underwent noninvasive screening and directed provocative testing on the basis of findings in the proband. Eighteen patients (mean±SD age, 41±17 years; 11 female) with unexplained cardiac arrest were assessed. The final diagnosis was catecholaminergic ventricular tachycardia (CPVT) in 10 patients (56%), Brugada syndrome in 2 patients (11%), and unexplained (idiopathic ventricular fibrillation) in 6 patients (33%). Of 55 family members (mean±SD age, 27±17 years; 33 female), 9 additional affected family members were detected from 2 families, with a single Brugada syndrome patient and 8 CPVT patients. Conclusions— Provocative testing with adrenaline and procainamide infusions is useful in unmasking the etiology of apparent unexplained cardiac arrest. This approach helps to diagnose primary electrical disease, such as CPVT and Brugada syndrome, and provides the opportunity for therapeutic intervention in identified, asymptomatic family members who harbor the same disease.

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Evaluation of QT interval duration and dispersion and proposed clinical criteria in diagnosis of long QT syndrome in patients with a genetically uniform type of LQT1

Abstract: Not all LQT1 patients can be distinguished from healthy relatives by assessment of QT duration or clinical criteria. Presence of LQT1 gene can carry the risk of cardiac events even with no or only marginal prolongation of QT interval.

Cited by 56 publications

References 23 publications

Systematic Assessment of Patients With Unexplained Cardiac Arrest

Systematic Assessment of Patients With Unexplained Cardiac Arrest

Restricting Excessive Cardiac Action Potential and QT Prolongation

Diagnosis of Unexplained Cardiac Arrest

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