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Repolarization syndromes

Early repolarization (ER), consisting of a J-point elevation, notching or slurring of the terminal portion of the R wave (J wave), and tall/symmetric T wave, is a common finding on the 12-lead electrocardiogram. For decades, it has been considered as benign, barring sporadic case reports and basic electrophysiology research that suggested a critical role of the J wave in the pathogenesis of idiopathic ventricular fibrillation (VF). In 2007-2008, a high prevalence of ER in patients with idiopathic VF was reported and subsequent studies reinforced the results. This PPT describes the current state of knowledge concerning ER syndrome associated with sudden cardiac death.

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Repolarization syndromes

  1. 1. REPOLARIZATION SYNDROMES Dr Ramachandra/Dr AN Patnaik
  2. 2. REPOLARIZATION SYNDROME Ventricular repolarisation is defined by the interval from the end of the QRS complex to the end of the T wave on surface ECG= J waves+ T +U waves+ ST segment. This phase of the cardiac cycle is subject to intrinsic and extrinsic influences; thereby, alterations noted in this phase can have Ventricular arrhythmias =repolarisation syndrome.
  3. 3. REPOLARIZATION SYNDROMES  1. ST-segment elevation a. Early repolarisation(elevated J point) b.Brugada syndrome  2. QT-interval abnormalities a. Short QT syndromes b. Long QT syndromes
  4. 4. EARLY REPOLARIZATION SYNDROME  J waves are found at the junction of the QRS complex and beginning of ST segment  Early repolarisation syndrome is an ECG finding consistent with J-point elevation(0.1-Mv) and prominent T waves usually associated with ST- segment elevation in 2 contiguous leads  It is not “normal variant” but linked to SCD and 2-5% general incidence.  Causes a.Extracardiac:Osborn waves,hypercalcemia, hypervagotonia, spinal cord injuries. b.Cardiac :Prinzmetal angina, acute transmural ischemia, and Brugada syndrome.
  5. 5. INCIDENCE  Incidence =2%-5%, most commonly seen in young, athletic, male and with stringent criterion (0.2-mV J-point elevation in 2 contiguous leads) drops the prevalence in the general population to 0.3%-0.8%.  ERP - increased risk of SCD is associated with J- point and ST-segment elevations limited to inferior and lateral leads on surface ECG  31% of patients with idiopathic VF  More at night in patients with VF, consistent with increased night-time vagal tone  Increased transmural dispersion of refractoriness in Phase 1-2 of the APD
  6. 6. INCIDENCE CONTD....  Inferior vs lateral leads/magnitude of J-point elevation (0.2 mV) are associated with a high risk of SCD(RR=2.98;95% CI=1.85-4.92; P 0.001)  EPS is unclear in risk stratification of such patients given low sensitivity (40%) and rate of VF inducibility.
  7. 7. GENETICS OF EARLY REPOLARIZATION SYNDROME  Phase 2 reentry likely mechanism of VF = increase in the activity of ITO, IKATP(KCNJ8), and IKACh  16% of ERPS and idiopathic VF had F/H of SCD
  8. 8. DIFFERENTIAL DIAGNOSIS CONDITIONS FEATURES Reversible causes of early repolarization pattern on ECG must be excluded, namely acute schemia, hypothermia, hypercalcemia, and irreversible spinal cord injuries and sympathetic nerve damage Vasospastic angina Mostly normal CAG Brugada syndrome limited to V1-V3 leads, Early repolarization pattern INF/Lateral leads and Ajmaline injection attenuates ERP.
  9. 9. CLASSIFICATION HAS BEEN PROPOSED FOR STRATIFYING ARRHYTHMIC RISK IN INDIVIDUALS OF ERP PATTERN  Type 1: The ERP only in the lateral leads= benign outcome=young, healthy men.  Type 2: ERP = inferior or inferolateral leads and is associated with moderate risk of Arrhythmic SCD, especially in individuals with syncope and personal or F/H of SCD.  Type 3: ERP = globally =inferior+ lateral+Rt precordial leads /highest risk of malignant ventricular arrhythmias, VT/VF storms, and sudden death.
  10. 10. TREATMENT  Pharmacologic:Quinidine, Intravenous Isoproterenol are useful.amiodarone, -blockers, and flecainide,are ineffective  ICD:Usuful for both for primary and secondary prevention of SCD along with Quinidine as adjuvant.
  11. 11. SUMMARY OF EARLY REPOLARIZATION SYNDROME  ERP pattern on ECG is not always a “benign variant,”  Careful assessment and close follow-up of H/O syncope/ERPS pattern.  A F/H of SCD is high risk.  Not a sensitive phenotypical marker for SCD, per se, but indicates a genetic predisposition toward the development of the same  Notched QRS complexes as markers of SCD.
  13. 13. BRUGADA SYNDROME  RBBB, ST-segment elevation and T inversion.  mutations in at least 8 separate genes encoding the sodium, potassium, and calcium channels involved in the generation of cardiac myocyte action potential  sudden cardiac death in up to 20%  (12/10,000) in Southeast Asia and less frequent cases (5/10,000) in the Western hemisphere  bangungut in Philippines, lai tai in Thailand, most common cause of SCD in young males in night
  14. 14. 3 DISTINCT ECG PATTERNS (V1-V3)  Type 1 pattern is characterized by J-point or coved ST-segment elevation 2 mm followed by a negative T wave.  Type 2 pattern is characterized by J-point or saddle-shaped St segment elevation 2 mm followed by positive or biphasic T wave.  Type 3 pattern is characterized by coved or saddle-shaped ST-segment elevation 1 mm.
  15. 15. BRUGADA ECG I J↑ >2mm T INV II J ↑2mm T Bipha sic III J↑ 1mm T Bipha sic
  16. 16. POSITIVE RESPONSE  A positive response to a sodium channel blocker is characterized by the following:  1. Type 1 coving ST-segment elevation in leadsV1-V2 or V3 (Fig 6).  2. Conversion of type 2 or type 3 to type 1 pattern.
  17. 17. GENETICS OF BRUGADA SYNDROME  autosomal-dominant, heterogeneous genetic disorder ,variable penetrance  MALE  Mutation(300 mutations) at the alpha-subunit of the sodium channel (SCNA5),K-channel(ITO),Ca channel seen.  loss of function of the sodium channel, is the most common genetic abnormality observed in up to 20% patients with BS  Spontaneous and inducible AF is noted in up to 20% of with biphasic P waves.
  19. 19.  Hallmark -heterogeneous shortening of the APD in the RV epicardium  A decrease in the inward Na and Ca currents coupled with a strong outward K current (ITO) toward the end of the phase 1 action potential results in the accentuation of the action potential notch and loss of action potential dome in some of the epicardium cells  Brugada ECG phenotype is a direct mmanifestation of the imbalance in ion currents during the latter portion of Phase 1 and prolonged phase 2 causing long APD.
  20. 20. CONTI..  electrical heterogeneity = electrical gradient Phase 2 reentry =of VT/VF  Predominance ITO in the epicardium, t repolarization in the epicardial cells recedes that in the M-cells (midmyocardial) and the endocardial cells, is responsible for the ST- segment elevation observed in the right Precordial leads in BS  The shortening of the APD secondary to enhanced vagal activity in association with Phase 3 afterdepolarizations may be responsible for the development of VF, a clinical scenario consistent with nocturnal deaths.
  21. 21. CLINICAL FEATURES  2 following groups: 1. Asymptomatic with Brugada ECG. 2. Symptomatic with Brugada ECG  ECG remains the cornerstone  The proposed clinical criteria for the diagnosis 1. Syncope with or without warning. 2. Seizures. 3. Nocturnal agonal respiration. 4. Family history of sudden cardiac death 40 years. 5. Brugada type 1 ECG in family member. 6. Documented VT/VF.
  22. 22. PHARMACOLOGIC DRUG CHALLENGE  Na channel-blocking - diagnostic /prognostic to reveal a concealed form of BS or convert type 2 or type 3 patterns to Brugada type 1 ECG.  Ajmaline, Procainamide, Flecainide, and Propafenone- challenge should be considered positive only when a type 1 ECG pattern (coved ST-segment elevation 2 mm with T-wave inversion in V1-V2 or V3)=8% event rate (ventricular arrhythmias, lethal and nonlethal) at 33 39 months of follow-up (hazard ratio 2.5)
  23. 23. PROGRAMMED ELECTRICAL STIMULATION  abnormal PES (inducible VT/VF) has a positive predictive value of 50% and a negative predictive value of 46% and is associated with increased risk of sudden cardiac death  Asymptomatic individuals with provoked type 1 ECG post-drug challenge with a negative electrical study (PES) have a good prognosis
  25. 25. RX  ICD remains the most effective treatment  20%-35% of inappropriate ICD shocks—most likely secondary to SVT(ST/ AF)  Drugs that modify the outward Na current in phase like Quinidine, an ITO blocker, is effective in ECG pattern normalization as well as in suppression of spontaneous and inducible VT/VF or Ca channel function promoter like Isoproteronal is useful.  RFA is used less frequent  Atrial fibrillation is treated with BB,Disopyramide and Quinidine.
  26. 26. SHORT QT SYNDROME  First description in 2000  Five genes encoding the potassium and calcium channels involved in generation of myocardial cell action potential= Gain of function  The gold standard for diagnosis remains a short QT interval on surface ECG  Only 27% of the patients with confirmed SQTS who underwent testing could be genetically classified.  The prevalence of SQTS (QTc 340 ms) in the general population is about 0.5%, making it a rare condition . DX; hypercalcemia, hyperthermia, and digitalis toxicity
  27. 27. CAUTION  The classic ECG: QTc interval of 360 ms, short ST segment, and tall T waves.  It is extremely crucial to record the heart rate at the time of QTc calculation, as the overcorrection of QTc and T-wave amplitude during bradycardia is well- known, the latter of which also increases at slower heart rates.  confirmed SQTS have a flat QTc/R-R interval relationship, whereby the QTc interval fails to prolong at slower heart rates and remains in the low range (ie, 360 ms at heart rates greater than 80 bpm).  Recording ECG at different heart rates with varying QTc intervals is helpful in separating a patient with “true SQTS” from a flat QTc/R-R interval response to
  29. 29. GENETICS OF SHORT QT SYNDROME  genetically heterogenous  mutations in 5 different genes encoding the potassium and calcium channels, gain of function involving the potassium channels is the major abnormality in the first 3 gene mutations  SQTS1-KCNH2 (hERG),=gain in function Ikr= ↓ APD and ↓ affinity to IKr blockers.  SQTS2 -KCNQ1= gain in function IKs= clinically associated with AF with SVR and SCD.  SQTS3-KCNI2,= gain in Iki.  CACNA1C and CACNB2b mutation for SQTS4 and SQTS5  only 27% confirmed SQTS genetically classified
  30. 30. RISK STRATIFICATION  D/D-hypercalcemia, hyperkalemia, Hypervagotonia, digitalis toxicity, hyperthermia  Ambulatory ECG recording is helpful not only to demonstrate a flat QTc/R-R,VT/VF/AF  Electrophysiologic study-short refractory periods (140-200 ms) in the atrium and ventricles during programmed stimulation helps confirm the underlying diagnosis and vulnerability of such patients toward spontaneous polymorphic VT/VF and AF.  PMVT/VF /AF is inducible in 60% in confirmed SQTS. sensitivity of inducing VF with hx of SCD 40% ,hence EPS is not final for Rx decision.
  31. 31. CLINICAL FEATURES To date, the largest database of patients in the world with confirmed SQTS comprises less than 60 patients.93 The most common first presentation is cardiac arrest, noted in 33% of the patients, with more than 60% having symptomatic history at the time of initial diagnosis. The initial age of presentation varies, ranging from 8 months to 70 years, with 80% of patients having a personal or family history of sudden cardiac death. The second most common presentation is syncope, noted in about 13% of patients, with the presumptive diagnosis of self-terminating VT episodes as the most likely cause of syncopal episodes. Isolated episodes of AF or atrial flutter, especially in young patients, are noted in about 17% of patients.
  32. 32. THERAPY OPTIONS Therapy options include ICD implant. Use of hydroquinidine is recommended to suppress recurrent VT/VF and also in patients deemed unsuitable for or who refuse an ICD implant
  33. 33. LONG QT SYNDROME  polymorphic VT  gold standard for DX= ECG  Exclude severe hypocalcemia/ hypokalemia, hypothermia/acute ischemia/CNS events, and drug effects  Prevalence=1:3000
  35. 35. ELECTROCARDIOGRAPHY  12-lead ECG -the gold standard  Bazett’s formula- most commonly used  Up to 460ms in women, 440ms in men –normal  An average of at least 5 cardiac cycles, in II, V5, and V6, and the longest QT any of these leads  Biphasic /notched/variations in amplitude and polarity (T-wave alternans)- is most commonly observed during exercise or emotional or physical stress and is a precursor to the development of polymorphic VT - regarded as a risk factor for sudden cardiac arrest and malignant VT.
  37. 37. MEASURE QTC
  39. 39. RX  Pharmacology BB, mexiletine  ICD  Cardiac arrest survivors.  On -blockers with recurrent syncope.  Age 5 years with syncope.  High-risk asymptomatic patients (J-LNS, marked QTc prolongation [550 ms], men with LQTS3, patients with 2 mutations who remain symptomatic despite -blocker therapy)  Combined=BB+ICD for daryprevention  Surgical -Left cardiac sympathetic denervation =removal of the first 4 thoracic ganglia
  40. 40. CONCLUSION Many have a molecular basis known & many will be discovered