Prevention of torsade de pointes in hospital settings: a scientific statement from the American Heart Association and the American College of Cardiology Foundation

Assessment of drug-induced torsade de pointes risk for hospitalized high-risk patients receiving QT-prolonging agents

BACKGROUND

Although risk factors for torsade de pointes (TdP) are known, identifying hospitalized patients at greatest risk for QTcP who should receive cardiac monitoring is poorly defined.

OBJECTIVES

Describe the prevalence of risk for TdP in patients and associations between risk factors and QTc prolongation (QTcP) at a tertiary teaching hospital.

METHODS

This retrospective analysis assessed physiological and pharmacological risk factors for TdP of adult patients receiving ≥1 QTc-prolonging medications (QTcMed) during hospitalization. The QTcMeds were stratified by risk for causing TdP (probable, possible, and conditional). Baseline electrocardiograms (ECGs) were assessed for QTcP associated with risk for TdP.

RESULTS

During a 6-month period, 12,401 (51%) hospitalizations received ≥1 QTcMed. A baseline ECG was obtained for 2381 (19%) patients. A total of 386 (16%) patients with a baseline ECG were found to have QTcP. Significant associations for QTcP were found with the following physiological risk factors: female (P = .021), left-ventricular ejection fraction <40% (P < .0001), cardiac arrest (P < .0001), and cardioversion (P = .007). Significantly more patients with QTcP (n = 209, 54%) received probable-risk QTcMeds than those without QTcP (n = 542, 27%; P < .0001). Probable-risk QTcMeds administered alone or concomitantly with other QTcMeds were more frequently associated with QTcP. No documented cases of TdP were identified.

CONCLUSIONS

Of the population receiving QTcMeds, only a small portion had a baseline ECG, identifying a large population at risk of QTcP without appropriate monitoring. Patients with cardiac disease receiving probable-risk QTcMeds were associated with the highest risk of QTcP and should be monitored closely.

Methadone, QTc prolongation and torsades de pointes: Current concepts, management and a hidden twist in the tale?

Methadone is a drug that has found widespread utility in the management of opioid addiction and pain. Along with its popularity, methadone has also earned an infamous reputation for causing prolongation of the QT interval and an increased risk of torsades de pointes. In this article we will give a brief overview of the long QT syndromes, followed by an in-depth look at the current pathophysiologic mechanisms of methadone induced QT prolongation, a review of the existing literature and the current concepts regarding the prevention and management of methadone induced torsades de pointes. In addition, we explore the idea and implications of a genetic link between methadone induced prolongation of the QT interval and torsades de pointes.

Flecainide associated torsade de pointes: A potential case of reverse use dependence

Flecainide has been known to cause torsades de pointes (TdP) in patients with structural heart disease and its mechanism has been attributed to use-dependency. We present a patient with flecainide-induced TdP in the absence of any other precipitating factors. This case highlights potential reverse use dependence associated with flecainide resulting in TdP.

The phenotype characteristics of type 13 long QT syndrome with mutation in KCNJ5 (Kir3.4-G387R)

BACKGROUND

Long QT syndrome type 13 (LQT13) is caused by loss-of-function mutation in the KCNJ5-encoded cardiac G-protein-coupled inward rectifier potassium channel subtype 4 protein. The electrocardiographic (ECG) features of LQT13 are not described yet.

OBJECTIVE

To describe for the first time in detail the phenotype-genotype relationship of the ECG and clinical features in patients with LQT13.

METHODS

The 12-lead ECGs, 24-hour Holter recordings, and clinical information from KCNJ5-G387R mutation carriers of a fourth-generation Han Chinese family with LQT13 and a group of healthy Chinese individuals were analyzed.

RESULTS

Compared with the analysis of the healthy group (n = 8), age- and sex-matched pair analysis revealed that the mutation carriers (n = 8) had ventricular repolarization abnormality results in the prolongation of corrected QT and QTpeak intervals (P < .01); greater combined measure of repolarization morphology (T-wave morphology combination score) based on asymmetry, flatness, and notch (P < .01); and reduced low frequency/high frequency ratio of heart rate variability (P < .01) as a reflection of cardiac autonomic imbalance. Mean heart rate, time domain parameters of heart rate variability, time interval from T-wave peak to T-wave end, and T-wave amplitude were similar.

CONCLUSIONS

This study demonstrates for the first time the ECG features of patients with LQT13. Our data suggest that QTpeak intervals and T-wave morphology combination score may be the better parameters than the corrected QT interval to predict the phenotype-genotype relationship in patients with LQT13.

Perioperative torsade de pointes: a systematic review of published case reports

BACKGROUND

Torsade de pointes is a rare but potentially fatal arrhythmia. More than 40 cases of perioperative torsade de pointes have been reported in the literature; however, the current evidence regarding this complication is very limited. To improve our understanding, we performed a systematic review and meta-analysis of all published case reports of perioperative torsade de pointes.

METHODS

MEDLINE was systematically searched for cases of perioperative torsade de pointes. We included patients of all age groups and cases that occurred from the immediate preoperative period to the third postoperative day. Patient and case characteristics as well as QT interval data were extracted.

RESULTS

Forty-six cases of perioperative torsade de pointes were identified; 29 occurred in women (67%), and 2 episodes were fatal (case fatality rate: 4%). Craniotomies and cardiac surgery accounted for 40% of all cases. Preceding events identified by the authors were hypokalemia (12/46, 26%; 99% confidence interval [CI], 9%-43%) and bradycardia (7/46, 15%; 99% CI, 2%-28%). Drugs were implicated in approximately one third of the events (14/46, 30%; 99% CI, 13%-48%). The mean corrected QT (QTc) at baseline was 457 ± 67 milliseconds (minimum 320 milliseconds; maximum 647 milliseconds; data available in 27/46 patients). At the time of the event, the mean QTc increased to 575 ± 77 milliseconds (minimum 413 milliseconds; maximum 766 milliseconds; data available in 33/46 patients). On average, QTc increased by +118 milliseconds (99% CI, 70-166 milliseconds; P < 0.001) between baseline and after the torsade de pointes event. All patients, except for 2, had a substantial prolongation of their QTc interval at the time of the event.

CONCLUSIONS

This systematic review identified several common risk factors for perioperative torsade de pointes. Given the nearly uniform presence of a substantial QTc interval prolongation at the time of a torsade de pointes episode, increased vigilance for perioperative QTc interval prolongation may be warranted.

Development and validation of a risk score to predict QT interval prolongation in hospitalized patients

BACKGROUND

Identifying hospitalized patients at risk for QT interval prolongation could lead to interventions to reduce the risk of torsades de pointes. Our objective was to develop and validate a risk score for QT prolongation in hospitalized patients.

METHODS AND RESULTS

In this study, in a single tertiary care institution, consecutive patients (n=900) admitted to cardiac care units comprised the risk score development group. The score was then applied to 300 additional patients in a validation group. Corrected QT (QTc) interval prolongation (defined as QTc>500 ms or an increase of >60 ms from baseline) occurred in 274 (30.4%) and 90 (30.0%) patients in the development group and validation group, respectively. Independent predictors of QTc prolongation included the following: female (odds ratio, 1.5; 95% confidence interval, 1.1-2.0), diagnosis of myocardial infarction (2.4 [1.6-3.9]), septic shock (2.7 [1.5-4.8]), left ventricular dysfunction (2.7 [1.6-5.0]), administration of a QT-prolonging drug (2.8 [2.0-4.0]), ≥2 QT-prolonging drugs (2.6 [1.9-5.6]), or loop diuretic (1.4 [1.0-2.0]), age >68 years (1.3 [1.0-1.9]), serum K⁺ <3.5 mEq/L (2.1 [1.5-2.9]), and admitting QTc >450 ms (2.3; confidence interval [1.6-3.2]). Risk scores were developed by assigning points based on log odds ratios. Low-, moderate-, and high-risk ranges of 0 to 6, 7 to 10, and 11 to 21 points, respectively, best predicted QTc prolongation (C statistic=0.823). A high-risk score ≥11 was associated with sensitivity=0.74, specificity=0.77, positive predictive value=0.79, and negative predictive value=0.76. In the validation group, the incidences of QTc prolongation were 15% (low risk); 37% (moderate risk); and 73% (high risk).

CONCLUSIONS

A risk score using easily obtainable clinical variables predicts patients at highest risk for QTc interval prolongation and may be useful in guiding monitoring and treatment decisions.

Prevalence and prognostic significance of long QT interval among patients with chest pain: selecting an optimum QT rate correction formula

BACKGROUND

Little is known about the prevalence and prognostic significance of long QT interval among patients with chest pain during the acute phase of suspected cardiovascular injury.

OBJECTIVES

Our aim was to investigate the prevalence and prognostic significance of long QT interval among patients presenting to the emergency department (ED) with chest pain using an optimum QT rate correction formula.

METHODS

We performed secondary analysis on data obtained from the IMMEDIATE AIM trial (N, 145). Data included 24-hour 12-lead Holter electrocardiographic recordings that were stored for offline computer analysis. The QT interval was measured automatically and rate corrected using seven QTc formulas including subject specific correction. The formula with the closer to zero absolute mean QTc/RR correlation was considered the most accurate.

RESULTS

Linear and logarithmic subject specific QT rate correction outperformed other QTc formulas and resulted in the closest to zero absolute mean QTc/RR correlations (mean±SD: 0.003±0.002 and 0.017±0.016, respectively). These two formulas produced adequate correction in 100% of study participants. Other formulas (Bazett's, Fridericia's, Framingham's, and study specific) resulted in inadequate correction in 47.6 to 95.2% of study participants. Using the optimum QTc formula, linear subject specific, the prevalence of long QTc interval was 14.5%. The QTc interval did not predict mortality or hospital admission at short and long term follow-up. Only the QT/RR slope predicted mortality at 7year follow-up (odds ratio, 2.01; 95% CI, 1.02-3.96; p<0.05).

CONCLUSIONS

Adequate QT rate correction can only be performed using subject specific correction. Long QT interval is not uncommon among patients presenting to the ED with chest pain.

Agreement between ICU clinicians and electrophysiology cardiologists on the decision to initiate a QTc-interval prolonging medication in critically ill patients with potential risk factors for torsade de pointes: a comparative, case-based evaluation

STUDY OBJECTIVES

To measure concordance between different intensive care unit (ICU) clinicians and a consensus group of electrophysiology (EP) cardiologists for use of a common rate-corrected QT interval (QTc)-prolonging medication in cases containing different potential risk factor(s) for torsade de pointes (TdP).

DESIGN

Prospective case-based evaluation.

SETTING

Academic medical center with 320 beds.

SUBJECTS

Medical house staff (MDs) and ICU nurses (RNs) from one center and select critical care pharmacists (PHs).

INTERVENTION

Completion of a survey containing 10 hypothetical ICU cases in which patients had agitated delirium for which a psychiatrist recommended intravenous haloperidol 5 mg every 6 hours. Each case contained different potential risk factor(s) for TdP in specific combinations. A group of five EP cardiologists agreed that haloperidol use was safe in five cases and not safe in five cases.

MEASUREMENTS AND MAIN RESULTS

For each case, participants were asked to document whether they would administer haloperidol, to provide a rationale for their decision, and to state their level of confidence in that decision. Most clinicians (92 of 115 [80%]) invited to participate completed the cases. Among the five cases where EP cardiologists agreed that haloperidol was not safe, 29% of respondents felt that haloperidol was safe. Conversely, in the five cases where EP cardiologists felt haloperidol was safe, 21% of respondents believed that it was not safe. Overall respondent-EP cardiologist agreement for haloperidol use across the 10 cases was moderate (κ = 0.51). MDs and PHs were in agreement with the EP cardiologists more than RNs (p=0.03). Interprofessional variability existed for the TdP risk factors each best identified. Clinician confidence correlated with EP cardiologist concordance for MDs (p=0.002) and PHs (p=0.0002), but not for RNs (p=0.69).

CONCLUSION

When evaluating use of a QTc interval-prolonging medication, ICU clinicians often fail to identify the TdP risk factors that EP cardiologists feel should prevent its use. Clinician-EP cardiologist concordance varies by the specific risk factor(s) for TdP and the ICU professional conducting the assessment.

Acquired long QT syndrome: frequency, onset, and risk factors in intensive care patients

BACKGROUND

Acquired long QT syndrome is a reversible condition that can lead to torsades de pointes and sudden cardiac death.

OBJECTIVE

To determine the frequency, onset, frequency of medications, and risk factors for the syndrome in intensive care patients.

METHODS

In a retrospective chart review of 88 subjects, hourly corrected QT intervals calculated by using the Bazett formula were collected. Acquired long QT syndrome was defined as a corrected QT of 500 milliseconds or longer or an increase in corrected QT of 60 milliseconds or greater from baseline level. Risk factors and medications administered were collected from patients' medical records.

RESULTS

The syndrome occurred in 46 patients (52%); mean time of onset was 7.4 hours (SD, 9.4) from time of admission. Among the 88 patients, 52 (59%) received a known QTc-prolonging medication. Among the 46 with the syndrome, 23 (50%) received a known QT-prolonging medication. No other risk factor studied was significantly predictive of the syndrome.

CONCLUSIONS

Acquired long QT syndrome occurs in patients not treated with a known QT-prolonging medication, indicating the importance of frequent QT monitoring of all intensive care patients.

Cardiovascular disease in women

Gender-specific data focused on cardiovascular disease (CVD) are becoming increasingly available. This is of great importance, given that CVD has become the number 1 killer of women, and unlike for men, mortality rates do not seem to be declining. Many factors are cited as the causes of sex-based differences, including delays in recognizing symptoms, underutilization of diagnostic tests and treatments, as well as anatomic, physiological, and genetic factors. Evidence of fundamental biological differences in vascular function and the underlying pathologic processes is only beginning to elucidated, motivated by growing evidence of differences in clinical presentations and outcomes between men and women. The good news is that we are starting to see improvements in outcomes for women, such as after coronary revascularization; decrease in complication rates with the advent of new techniques, such as radial access for cardiac catheterizations; as well as increased participation of women in clinical trials. The underlying mechanisms of ischemic heart disease remain to be elucidated, and will help guide therapy and ultimately may explain the higher prevalence of : subendocardial myocardial infarctions, spontaneous arterial dissections, plaque erosion, increased vasospastic disorders, such as coronary microvascular disease, and pulmonary hypertension in women compared with men. We have made great progress in understanding gender-related differences in CVDs, but much remains to be done to optimize the prevention of CVD for both men and women.

Antipsychotic Prescribing Patterns, and the Factors and Outcomes Associated with Their Use, among Patients Requiring Prolonged Mechanical Ventilation in the Long-Term Acute Care Hospital Setting

BACKGROUND:

Administration of scheduled antipsychotic therapy to mechanically ventilated patients to prevent or treat delirium is common, despite the lack of evidence to support its use. Among long-term acute care hospital (LTACH) patients requiring prolonged mechanical ventilation (PMV), the frequency of scheduled antipsychotic therapy use, and the factors and outcomes associated with it, have not been described.

OBJECTIVE:

To identify scheduled antipsychotic therapy prescribing practices, and the factors and outcomes associated with the use of antipsychotics, among LTACH patients requiring PMV.

METHODS:

Consecutive patients without major psychiatric disorders or dementia who were admitted to an LTACH for PMV over 1 year were categorized as those receiving scheduled antipsychotic therapy (≥24 hours of use) and those not receiving scheduled antipsychotic therapy. Presence of delirium, use of psychiatric evaluation, nonscheduled antipsychotic therapy, and scheduled antipsychotic therapy—related adverse effects were extracted and compared between the 2 groups and when significant (p ≤ 0.05), were entered into a regression analysis using generalized estimating equation techniques.

RESULTS:

Among 80 patients included, 39% (31) received scheduled antipsychotic therapy and 61% (49) did not. Baseline characteristics, including age, sex, illness severity, and medical history, were similar between the 2 groups. Scheduled antipsychotic therapy was administered on 52% of LTACH days for a median (interquartile range [IQR]) of 25 (6–38) days and, in the antipsychotic group, was initiated at an outside hospital (45%) or on day 2 (1–6; median [IQR]) of the LTACH stay (55%). Quetiapine was the most frequently administered scheduled antipsychotic (77%; median dose 50 [37–72] mg/day). Use of scheduled antipsychotic therapy was associated with a greater incidence of psychiatric evaluation (OR 5.7; p = 0.01), delirium (OR 2.4; p = 0.05), as-needed antipsychotic use (OR 4.1; p = 0.005) and 1:1 sitter use (OR 7.3; p = 0.001), but not benzodiazepine use (p = 0.19).

CONCLUSIONS:

Among LTACH patients requiring PMV, scheduled antipsychotic therapy is used frequently and is associated with a greater incidence of psychiatric evaluation, delirium, as-needed psychotic use, and sitter use. Although scheduled antipsychotic therapy—related adverse effects are uncommon, these effects are infrequently monitored.

Multi-factorial causes of torsade de pointes in a hospitalised surgical patient

A 55-year-old chronic alcoholic male known to be positive for human immunodeficiency virus (HIV) was admitted to a surgical ward following perianal abscess drainage. He was noted to have sinus bradycardia, ventricular premature complexes, and mild hypotension. His laboratory investigations revealed mild hypokalaemia. He was intermittently agitated and alcohol withdrawal syndrome (AWS) was diagnosed. Postoperatively, he received intravenous piperacillin/tazobactam and metronidazole infusions along with a small dose of dopamine. Analysis of a 24-hour Holter monitor (ECG) showed a prolonged QT interval with two episodes of self-terminating torsade de pointes. His AWS was treated, hypokalaemia was corrected, and dopamine, along with antibiotics, was withdrawn. There was no recurrence of arrhythmias. This case highlights the importance of avoiding QT-prolonging drugs in hospitalised patients, since hospitalised patients often have multiple risk factors for a proarrhythmic response.

Effect of combined fluoroquinolone and azole use on QT prolongation in hematology patients

QTc prolongation is a risk factor for development of torsades de pointes (TdP). Combination therapy with fluoroquinolones and azoles is used in patients with hematologic malignancies for prophylaxis and treatment of infection. Both drug classes are implicated as risk factors for QTc prolongation. The cumulative effect on and incidence of QTc prolongation for this combination have not been previously described. A retrospective chart review was performed with hospitalized inpatients from 1 September 2008 to 31 January 2010 comparing QTc interval data from electrocardiogram (ECG) assessment at baseline and after the initiation of combination therapy. Ninety-four patients were eligible for inclusion. The majority, 88 patients (93.6%), received quinolone therapy with levofloxacin. Fifty-three patients (56.4%) received voriconazole; 40 (42.6%) received fluconazole. The overall mean QTc change from baseline was 6.1 (95% confidence interval [CI], 0.2 to 11.9) ms. Twenty-one (22.3%) of the studied patients had clinically significant changes in the QTc while receiving combination fluoroquinolone-azole therapy. Statistically significant risk factors for clinically significant changes in QTc were hypokalemia (P = 0.03) and a left-ventricular ejection fraction of <55% (P = 0.02). Low magnesium (P = 0.11), exposure to 2 or more drugs with the potential to prolong the QTc interval (P = 0.17), and female sex (P = 0.21) trended toward significance. Combination therapy with fluoroquinolone and azole antifungals is associated with increased QTc from baseline in hospitalized patients with hematologic malignancies. One in five patients had a clinically significant change in the QTc, warranting close monitoring and risk factor modification to prevent the possibility of further QTc prolongation and risk of TdP.

Ventricular arrhythmias in patients with implanted cardioverter defibrillators

Implantable cardioverter-defibrillators (ICDs) are highly effective in reducing mortality related to ventricular arrhythmias. However, there is considerable morbidity associated with their use, mostly related to ICD shocks. In addition, the occurrence of arrhythmias and ICD shocks in patients with heart failure is associated with an adverse prognosis. Strategies to reduce or prevent ventricular arrhythmias and shocks are a prime area of focus and development in patients with ICDs.

Postoperative QT interval prolongation in patients undergoing noncardiac surgery under general anesthesia

BACKGROUND

Abnormal cardiac repolarization, indicated by a prolongation of the QT interval, increases the risk for torsades de pointes, a potentially life-threatening arrhythmia. Many perioperatively administered drugs and conditions prolong the QT interval. Despite several reports of perioperative torsades de pointes, systematic evidence regarding perioperative QT interval prolongation is limited.

METHODS

Serial postoperative 12-lead electrocardiograms were obtained from 469 adult patients undergoing major noncardiac surgery under general anesthesia. Heart rate corrected QT-interval duration (Fridericia formula) was the primary outcome. All perioperatively administered drugs were recorded. Emphasis was placed on absolute QTc prolongation greater than 500 ms and relative increases of 30 and 60 ms.

RESULTS

At the end of surgery, 80% of the patients (345 of 429) experienced a significant QTc interval prolongation (ΔQTc 23 ± 26 ms (mean and SD), 95% CI 20-25 ms, P less than 0.001). Approximately 51% (219 of 429) had a QTc greater than 440 ms, and 4% (16 of 429) a QTc greater than 500 ms. In 39% (166 of 429), the ΔQTc was greater than 30 ms, in 8% (34 of 429) >60 ms, and in greater than 0.5% (2 of 429) >100 ms. No changes in ΔQTc occurred at subsequent time points. One patient developed torsades de pointes with a ΔQTc: 29 ms (0.4% incidence rate). Several drugs had a large effect on ΔQTc: isoflurane, methadone, ketorolac, cefoxitin, zosyn, unasyn, epinephrine, ephedrine, and calcium. Postoperative body temperature had a weak negative correlation with ΔQTc (r = -0.15, P = 0.02); serum magnesium, potassium, and calcium concentrations were not correlated.

CONCLUSION

Postoperative QT-interval prolongation is common. Several perioperatively administered drugs are associated with a substantial QT-interval prolongation. The exact cause and its clinical relevance are, however, unclear. Nevertheless, an association between postoperative QT prolongation and risk for torsades de pointes is likely.

Increased incidence of QT interval prolongation in a population receiving lower doses of methadone maintenance therapy

AIMS

The aim of this study was to investigate the frequency of corrected QT interval (QTc) prolongation in a methadone maintenance therapy (MMT) population, and to examine potential associations between this QTc interval and methadone dose as well as concurrent use of opiates, cocaine and benzodiazepines.

DESIGN

Cross-sectional study of patients attending a specialist drug treatment clinic from July 2008 to January 2009.

SETTING

Single-centre inner-city specialist drug treatment clinic, Ireland.

PARTICIPANTS

A total of 180 patients on stable MMT attending for daily methadone doses, over a 6-month period, where a total of 376 patients were attending during the study period.

MEASUREMENTS

All patients agreeing to participate in the study underwent 12-lead electrocardiograms and QTc analysis, as well as analysis of urine toxicology screen results for opiates, benzodiazepines and cocaine. ECGs were carried out prior to methadone dose being received, regardless of time of day (trough ECG).

FINDINGS

The average age was 32.6 ± 7.1 years, with mean [standard deviation (SD)] methadone dose 80.4 ± 27.5 mg. The mean (SD) QTc was 420.9 ± 21.1 ms, range 368-495 ms. Patients who had a positive toxicology screen for opiates were receiving significantly lower doses of methadone (77.8 ± 23.5 mg versus 85.0 ± 21.4 mg, P = 0.04). No significant association was noted between QTc interval prolongation and presence of cocaine metabolites in the urine (P = 0.13) or methadone dose (P = 0.33). 8.8% of patients had evidence of prolonged QTc interval (8.3% male QTc ≥ 450 ms and 0.5% female QTc ≥ 470 ms), with 11.1% (n = 20) having QTc intervals > 450 ms.

CONCLUSIONS

Drug-induced corrected QT interval prolongation is evident (ranging from 8.8-11.1%, depending on definition applied) in patients receiving relatively low daily doses of methadone therapy, with no evidence of a dose-response relationship. The presence of cocaine metabolites in urine does not appear to be associated with increased corrected QT interval. Increased awareness of cardiac safety guidelines, including relevant clinical and family history, baseline and trough dose ECG monitoring, should be incorporated into methadone maintenance therapy protocols.

Clinical Experience with Ranolazine in a Veteran Population with Chronic Stable Angina

BACKGROUND:

Efficacy of ranolazine in the treatment of chronic stable angina (CSA) has been established; however, pivotal trials did not require the optimization of conventional antianginal drug therapy (CADT) prior to use in a veteran population.

OBJECTIVE:

To determine whether ranolazine, when added to optimized doses of CADT, improves angina in a veteran population with CSA and refractory symptoms.

METHODS:

In an observational retrospective study, 35 patients prescribed ranolazine and having a baseline Seattle Angina Questionnaire (SAQ) administered at a Veterans Affairs medical center in Gainesville, FL, were evaluated. Patients who were prescribed ranolazine by a provider from outside the institution and did not obtain a baseline SAQ were excluded. The primary outcome measure was the change in SAQ scores from baseline to 1 and 3 months after initiation of ranolazine treatment. Secondary measures included clinically significant QTc interval prolongation (>500 msec or an increase of at least 60 msec from baseline), adverse drug reactions, discontinuation rates, and drug-drug interactions.

RESULTS:

The addition of ranolazine to optimized CADT was associated with improvement in all dimensions of the SAQ scores at 1 and 3 months compared to baseline scores (p < 0.001 for all dimensions). Mean changes in SAQ dimension scores at 1 and 3 months, respectively, were as follows: physical limitation, +9.86 and +11.94; angina stability, +39.29 and +32.69; angina frequency, +26.79 and +25.38; treatment satisfaction, +11.38 and +10.66; and disease perception, +16.85 and +18.59. Improvments in all dimensions, except treatment satisfaction, were clinically significant as defined by set criteria. Of the 7 patients whose ranolazine dosages were increased to 1000 mg twice daily, only 2 patients were able to maintain treatment at that dosage.

CONCLUSIONS:

Ranolazine added to optimized doses of CADT demonstrated an improvement in angina symptoms when given to a veteran population with persistent CSA.

A 26-year-old woman with recurrent loss of consciousness

The case of a 26-year-old woman with congenital long QT syndrome and recurrent arrhythmic syncope which had been misdiagnosed as a seizure disorder is presented. Useful criteria for discriminating between loss of consciousness due to congenital long QT syndrome and loss of consciousness caused by seizure activity are discussed. The multiple potential causes and clinical implications of a prolonged QT interval, as well as the clinical features and management of congenital long QT syndrome are reviewed.

Microvolt T-wave alternans physiological basis, methods of measurement, and clinical utility--consensus guideline by International Society for Holter and Noninvasive Electrocardiology

This consensus guideline was prepared on behalf of the International Society for Holter and Noninvasive Electrocardiology and is cosponsored by the Japanese Circulation Society, the Computers in Cardiology Working Group on e-Cardiology of the European Society of Cardiology, and the European Cardiac Arrhythmia Society. It discusses the electrocardiographic phenomenon of T-wave alternans (TWA) (i.e., a beat-to-beat alternation in the morphology and amplitude of the ST-segment or T-wave). This statement focuses on its physiological basis and measurement technologies and its clinical utility in stratifying risk for life-threatening ventricular arrhythmias. Signal processing techniques including the frequency-domain Spectral Method and the time-domain Modified Moving Average method have demonstrated the utility of TWA in arrhythmia risk stratification in prospective studies in >12,000 patients. The majority of exercise-based studies using both methods have reported high relative risks for cardiovascular mortality and for sudden cardiac death in patients with preserved as well as depressed left ventricular ejection fraction. Studies with ambulatory electrocardiogram-based TWA analysis with Modified Moving Average method have yielded significant predictive capacity. However, negative studies with the Spectral Method have also appeared, including 2 interventional studies in patients with implantable defibrillators. Meta-analyses have been performed to gain insights into this issue. Frontiers of TWA research include use in arrhythmia risk stratification of individuals with preserved ejection fraction, improvements in predictivity with quantitative analysis, and utility in guiding medical as well as device-based therapy. Overall, although TWA appears to be a useful marker of risk for arrhythmic and cardiovascular death, there is as yet no definitive evidence that it can guide therapy.

Prolonged corrected QT interval in anti-Ro/SSA-positive adults with systemic lupus erythematosus

OBJECTIVE

To examine whether anti-Ro/SSA antibodies are associated with an increased risk of corrected QT (QTc) prolongation, and to study the stability of this relationship over time.

METHODS

Patients fulfilling the American College of Rheumatology (ACR) criteria for systemic lupus erythematosus (SLE) were invited to undergo a 12-lead resting electrocardiogram (EKG) in the pilot phase of our project, performed between February 2002 and March 2005. The same study population was used to perform a second similar analysis with a larger sample between April 2005 and May 2007. Multivariate logistic regression models were fit to estimate the cross-sectional association between anti-Ro/SSA and other demographic and clinical variables on QTc prolongation. The other potentially associated factors examined included age, sex, disease duration, lupus activity (Systemic Lupus Erythematosus Disease Activity Index 2000 update), damage (Systemic Lupus International Collaborating Clinics/ACR Damage Index), potassium and magnesium levels, and medications with the potential to prolong the QTc interval.

RESULTS

Cross-sectional analysis of the pilot data (n = 150 patients) showed an association of prolonged QTc with the presence of anti-Ro/SSA (adjusted odds ratio [OR] 12.6; 95% confidence interval [95% CI] 2.3, 70.7). In the second larger study (n = 278), the association was replicated, with a narrower 95% CI (adjusted OR 5.1; 95% CI 1.5, 17.4). In the 118 patients with 2 EKG assessments, the results were consistent over time.

CONCLUSION

Anti-Ro/SSA was associated with QTc prolongation in both our pilot data and a larger SLE cohort sample. Patients positive for anti-Ro/SSA may benefit from EKG testing and appropriate counseling should be considered for those identified with QTc prolongation.

Causes and management of drug-induced long QT syndrome

Long QT syndrome (LQTS) is characterized by inherited or acquired prolonged QT interval on the surface electrocardiogram. This can lead to torsade de pointes ventricular tachycardia (TdP VT) and ventricular fibrillation. In the acquired form of the disease, medications from several classes can cause TdP VT or potentiate the electrocardiographic findings. These include class IA and III antiarrhythmics, antibiotics (macrolides and quinolones), antidepressants (tricyclics and selective serotonin reuptake inhibitors), antipsychotics (haloperidol and phenothiazines), and antiemetics (ondansetron and prochlorperazine). We present four cases of drug-induced LQTS resulting in life-threatening cardiac arrhythmias. Antiarrhythmic medications were the cause in two cases, and the other two cases involved noncardiac medications. All four patients had at least one risk factor for LQTS in addition to the offending drug, including female gender, hypokalemia, hypomagnesemia, and bradycardia. In one patient, amiodarone was administered for treatment of VT, although the correct diagnosis was actually TdP VT. In patients with polymorphic VT or ventricular fibrillation without a significant history of cardiovascular disease, drug-induced LQTS should be high in the differential diagnosis. Prompt diagnosis is key, as amiodarone, while often used to suppress VT, is potentially harmful in the setting of LQTS and TdP VT.

How many patients need QT interval monitoring in critical care units? Preliminary report of the QT in Practice study

Recent Scientific Statement from the American Heart Association (AHA) recommends that hospital patients should receive QT interval monitoring if certain conditions are present: QT-prolonging drug administration or admission for drug overdose, electrolyte disturbances (K, Mg), and bradycardia. No studies have quantified the proportion of critical care patients that meet the AHA's indications for QT interval monitoring. This is a prospective study of 1039 critical care patients to determine the proportion of patients that meet the AHA's indications for QT interval monitoring. Secondary aim is to evaluate the predictive value of the AHA's indications in identifying patients who actually develop QT interval prolongation.

METHODS

Continuous QT interval monitoring software was installed in all monitored beds (n = 154) across 5 critical care units. This system uses outlier rejection and median filtering in all available leads to construct an root-mean-squared wave from which the QT measurement is made. Fridericia formula was used for heart rate correction. A QT interval greater than 500 milliseconds for 15 minutes or longer was considered prolonged for analyses. To minimize false positives all episodes of QT prolongation were manually over read. Clinical data was abstracted from the medical record.

RESULTS

Overall 69% of patients had 1 or more AHA indications for QT interval monitoring. More women (74%) had indications than men (64%, P = .001). One quarter (24%) had QT interval prolongation (>500 ms for ≥15 minutes). The odds for QT interval prolongation increased with the number of AHA indications present; 1 indication, odds ratio (OR) = 3.2 (2.1-5.0); 2 indications, OR = 7.3(4.6-11.7); and 3 or more indications OR = 9.2(4.8-17.4). Positive predictive value of the AHA indications for QT interval prolongation was 31.2%; negative predictive value was 91.3%.

CONCLUSION

Most critically ill patients (69%) have AHA indications for QT interval monitoring. One quarter of critically ill patients (24%) developed QT interval prolongation. The AHA indications for QT interval monitoring successfully captured the majority of critically ill patients developing QT interval prolongation.

Torsades: adjacent and triggering electrocardiographic events

Torsades de pointes (TdP) is a particular variant of ventricular arrhythmia associated with the long QT syndrome. The background of the latter is essentially 2-fold: patients under treatment with QT-prolonging drugs and subjects with congenital ionopathies. A third category is composed of subjects with both of these backgrounds. The fundamental feature of TdP is its provocation by pause-related augmentation of the repolarizing TU wave. The substrate electrocardiogram (ECG) shows prominent U waves in regular rhythm. The exaggeration of the U wave voltage following a pause is more marked the longer the pause and, for a given pause, more marked the faster the prepause rate. The pause-related sequences figure frequently adjacent to that which actually triggers the attack of TdP and continues to be seen after the event, serving to advise the physician as to the diagnosis, even following cardiac resuscitation, so that preventive measures can be taken (pacing, intravenous magnesium sulfate, or infusion with isoproterenol). The U wave of the regular rhythm ECG may show amplitude instability: an especially tall U triggering a premature ventricular complexe (PVC) that then in turn generates a pause-related sequence. TU alternans is common. Because these patients may not be in a monitored bed, recognition of pause-related phenomena in a patient with a long QT requires the ECG reader of the day to alert the floor as to the running danger. The mechanism of the pause-related TU augmentation is the generation of early afterdepolarizations.

Recent advances in the management of chronic stable angina II. Anti-ischemic therapy, options for refractory angina, risk factor reduction, and revascularization

The objectives in treating angina are relief of pain and prevention of disease progression through risk reduction. Mechanisms, indications, clinical forms, doses, and side effects of the traditional antianginal agents - nitrates, β-blockers, and calcium channel blockers - are reviewed. A number of patients have contraindications or remain unrelieved from anginal discomfort with these drugs. Among newer alternatives, ranolazine, recently approved in the United States, indirectly prevents the intracellular calcium overload involved in cardiac ischemia and is a welcome addition to available treatments. None, however, are disease-modifying agents. Two options for refractory angina, enhanced external counterpulsation and spinal cord stimulation (SCS), are presented in detail. They are both well-studied and are effective means of treating at least some patients with this perplexing form of angina. Traditional modifiable risk factors for coronary artery disease (CAD) - smoking, hypertension, dyslipidemia, diabetes, and obesity - account for most of the population-attributable risk. Individual therapy of high-risk patients differs from population-wide efforts to prevent risk factors from appearing or reducing their severity, in order to lower the national burden of disease. Current American College of Cardiology/American Heart Association guidelines to lower risk in patients with chronic angina are reviewed. The Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation (COURAGE) trial showed that in patients with stable angina, optimal medical therapy alone and percutaneous coronary intervention (PCI) with medical therapy were equal in preventing myocardial infarction and death. The integration of COURAGE results into current practice is discussed. For patients who are unstable, with very high risk, with left main coronary artery lesions, in whom medical therapy fails, and in those with acute coronary syndromes, PCI is indicated. Asymptomatic patients with CAD and those with stable angina may defer intervention without additional risk to see if they will improve on optimum medical therapy. For many patients, coronary artery bypass surgery offers the best opportunity for relieving angina, reducing the need for additional revascularization procedures and improving survival. Optimal medical therapy, percutaneous coronary intervention, and surgery are not competing therapies, but are complementary and form a continuum, each filling an important evidence-based need in modern comprehensive management.