The U-wave: A remaining enigma of the electrocardiogram

The U-wave's electrophysiological origin remains unknown and is subject to debate. It is rarely used for diagnosis in clinical practice. The aim of this study was to review new information regarding the U-wave. Further to present the proposed theories behind the U-wave's origin along with potential pathophysiologic and prognostic implications related to its presence, polarity and morphology.

METHOD

Literature searches were conducted to retrieve publications related to the electrocardiogram U-wave in the literature database Embase.

RESULTS

The review of the literature revealed the following major theories that will be discussed; late depolarisation, delayed or prolonged repolarisation, electro-mechanical stretch and IK1 dependent intrinsic potential differences in the terminal part of the action potential. Various pathologic conditions were found to correlate with the presence and properties of the U-wave, such as its amplitude and polarity. Abnormal U-waves can, for example, be observed in coronary artery disease with ongoing myocardial ischemia or infarction, ventricular hypertrophy, congenital heart disease, primary cardiomyopathy and valvular defects. Negative U-waves are highly specific for the presence of heart diseases. Concordantly negative T- and U-waves are especially associated with cardiac disease. Patients with negative U-waves tend to have higher blood pressure and history of hypertension, higher heart rate, cardiac disease and left ventricular hypertrophy compared to subjects with normal U-waves. Negative U-waves have been found to be associated with increased risk of all-cause mortality, cardiac death and cardiac hospitalisation in men.

CONCLUSIONS

The origin of the U-wave is still not established. U-wave diagnostics may reveal cardiac disorders and the cardiovascular prognosis. Including the U-wave characteristics in the clinical ECG assessment may be useful.

Verinurad does not prolong QTc interval: a thorough QT study using concentration-QTc modelling

AIM

This thorough QT/QTc (TQT) study was conducted to evaluate the risk of QT prolongation for verinurad when combined with allopurinol. Verinurad is a novel, urate anion exchanger 1 inhibitor that reduces serum urate levels by promoting urinary excretion of uric acid. It is co-administered with a xanthine oxidase inhibitor.

METHODS

The TQT study (NCT04256629) was a randomized, placebo-controlled, double-blind, three-period, crossover study, conducted in healthy volunteers. A total of 24 participants received single doses of verinurad 24 mg extended release, 40 mg immediate release formulation (both co-administered with allopurinol 300 mg), and matching placebos. The primary endpoint was baseline- and placebo-adjusted Fridericia-corrected QTcF interval (ΔΔQTcF) at the concentration of interest. A prespecified linear mixed-effects concentration-QTc model was used to estimate the primary endpoint. Time-matched 12-lead digital electrocardiograms and plasma concentrations were measured at baseline and up to 48 h after dose in each participant.

RESULTS

Estimated ΔΔQTcF at the highest clinically relevant scenario (76 ng/mL) was -2.7 msec (90% confidence interval [CI]: -4.6, -0.8). Furthermore, the upper 90% ΔΔQTcF CI was estimated to be below 10 msec at all observed verinurad concentrations. Supratherapeutic verinurad dose was used to achieve exposures eightfold higher than the highest clinically relevant exposure, thus waiving the need for positive control.

CONCLUSIONS

As the effect on ΔΔQTcF was below the threshold for regulatory concern (10 msec) at the supratherapeutic exposure, it can be concluded that verinurad and allopurinol treatment does not induce QTcF prolongation at the highest clinically relevant exposures.

The cancer patient and cardiology

Advances in cancer treatments have improved clinical outcomes, leading to an increasing population of cancer survivors. However, this success is associated with high rates of short- and long-term cardiovascular (CV) toxicities. The number and variety of cancer drugs and CV toxicity types make long-term care a complex undertaking. This requires a multidisciplinary approach that includes expertise in oncology, cardiology and other related specialties, and has led to the development of the cardio-oncology subspecialty. This paper aims to provide an overview of the main adverse events, risk assessment and risk mitigation strategies, early diagnosis, medical and complementary strategies for prevention and management, and long-term follow-up strategies for patients at risk of cancer therapy-related cardiotoxicities. Research to better define strategies for early identification, follow-up and management is highly necessary. Although the academic cardio-oncology community may be the best vehicle to foster awareness and research in this field, additional stakeholders (industry, government agencies and patient organizations) must be involved to facilitate cross-discipline interactions and help in the design and funding of cardio-oncology trials. The overarching goals of cardio-oncology are to assist clinicians in providing optimal care for patients with cancer and cancer survivors, to provide insight into future areas of research and to search for collaborations with industry, funding bodies and patient advocates. However, many unmet needs remain. This document is the product of brainstorming presentations and active discussions held at the Cardiovascular Round Table workshop organized in January 2020 by the European Society of Cardiology.

Drug-induced myocardial dysfunction - recommendations for assessment in clinical and pre-clinical studies

Introduction: Drug-induced myocardial dysfunction is an important safety concern during drug development. Oncology compounds can cause myocardial dysfunction, leading to decreased left ventricular ejection fraction and heart failure via several mechanisms. Cardiovascular imaging has a major role in the early detection and monitoring of cardiotoxicity. Echocardiography is the method of choice because of its widespread availability, low cost, and absence of radiation exposure. Cardiac magnetic resonance imaging can provide better reliability, reproducibility, and accuracy in the detection of drug-induced myocardial dysfunction. In addition, it enables assessment of myocardial edema, fibrosis, and necrosis. Cardiac serologic biomarkers such as troponins and B-type natriuretic peptides are used in combination with imaging during drug development. This article provides a general overview of each imaging modality and practical guidance for early detection and monitoring of cardiotoxicity.Areas covered: Cardiovascular imaging modalities and cardiac biomarkers for monitoring of cardiac function and early detection of drug-induced myocardial dysfunction in drug development.Expert opinion: Some new drugs especially in the oncology field, can cause myocardial dysfunction. Depending on the strength of pre-clinical or clinical data, CV imaging modalities and cardiac biomarkers play an important role in the early detection and mitigation plans for such drugs during their development.

Ticagrelor does not impact patient-reported pain in young adults with sickle cell disease: a multicentre, randomised phase IIb study

Ticagrelor is an antiplatelet agent for adults with coronary artery disease. The inhibition of platelet activation may decrease the frequency of vaso-occlusion crisis (VOC) in sickle cell disease (SCD). The HESTIA2 study (NCT02482298) randomised 87 adults with SCD (aged 18-30 years) 1:1:1 to twice-daily ticagrelor 10, 45 mg or placebo for 12 weeks. Numerical decreases from baseline in mean proportion of days with patient-reported pain (primary endpoint) were seen in all three groups, as well as in pain intensity and analgesic use, with no significant differences between placebo and ticagrelor treatment groups. Plasma ticagrelor concentrations and platelet inhibition increased with dose. Adverse events were distributed evenly across groups and two non-major bleeding events occurred per group. Ticagrelor was well tolerated with a low bleeding risk, but no effect on diary-reported pain was detected. Potential effects on frequency of VOCs will need to be evaluated in a larger and longer study.

Drug-induced blood pressure increase - recommendations for assessment in clinical and non-clinical studies

INTRODUCTION

Changes in blood pressure (BP) are now proactively examined throughout the drug development process as an integral aspect of safety monitoring. This is because hypertension is a very strong risk factor for cardiovascular events and drug-induced increases in BP have attracted increased regulatory attention. However, there is currently no guidance from regulatory agencies on the minimum BP data required for submissions, and there are no specific criteria for what constitutes a safety signal for increased BP in non clinical studies. Areas covered: Evaluation of BP increases through the drug discovery and development process. Expert opinion: Research into the effects of drugs should begin before clinical development is initiated and continue throughout the clinical trial program. Non clinical studies should inform a benefit-risk analysis that will aid decision-making of whether to enter the drug into Phase I development. The degree of acceptable risk will vary according to the therapy area, treatment indication and intended population for the new drug, and the approach to BP assessment and risk mitigation should be tailored accordingly. However, BP monitoring should always be included in clinical trials, and data collected from multiple studies, to convincingly prove or refute a suspicion of BP effects.

Evaluation of the effect of Naloxegol on cardiac repolarization: a randomized, placebo- and positive-controlled crossover thorough QT/QTc study in healthy volunteers

BACKGROUND

Opioid-induced constipation (OIC) is a common adverse effect associated with opioid use. Naloxegol is a PEGylated derivative of naloxone in clinical development as a once-daily oral treatment of OIC.

OBJECTIVES

A thorough QT/QTc study was conducted, according to International Conference on Harmonisation E14 guidelines, to characterize the effect of naloxegol on cardiac repolarization.

METHODS

In this randomized, positive- and placebo-controlled crossover study, healthy men received a single dose of naloxegol 25 mg (therapeutic dose), naloxegol 150 mg (supratherapeutic dose), moxifloxacin 400 mg (positive control), or placebo in 1 of 4 sequences (Williams Latin square design). The washout time between treatment periods was at least 5 days. Digital 12-lead ECGs were recorded at baseline and at 10 time points over 24 hours after dosing in each treatment period. QT intervals were corrected for heart rate using the Fridericia formula (QTcF) and the Bazett formula (QTcB).

RESULTS

A total of 52 subjects were enrolled (mean age, 28 years), and 45 received all 4 treatments. The placebo-corrected, baseline-adjusted, mean increases in QTcF with naloxegol 25 and 150 mg were both <5 msec at each time point, and all upper limits of the 2-sided 90% CI were <10 msec. Similar findings were observed using QTcB; the upper limits of the 2-sided 90% CI were <10 msec at all time points after dosing with naloxegol 25 or 150 mg. With moxifloxacin 400 mg, mean QTcF was increased by a maximum of 11.1 msec (90% CI, 9.3-12.9 msec), supporting assay sensitivity.

CONCLUSION

Naloxegol at 25 and 150 mg was not associated with QT/QTc interval prolongation in these healthy men, and at the proposed therapeutic dose of 25 mg/d, naloxegol is not expected to have a clinically relevant effect on cardiac repolarization in patients with OIC. ClinicalTrials.gov identifier: NCT01325415.

The evaluation and management of drug effects on cardiac conduction (PR and QRS intervals) in clinical development

Recent advances in electrocardiographic monitoring and waveform analysis have significantly improved the ability to detect drug-induced changes in cardiac repolarization manifested as changes in the QT/corrected QT interval. These advances have also improved the ability to detect drug-induced changes in cardiac conduction. This White Paper summarizes current opinion, reached by consensus among experts at the Cardiac Safety Research Consortium, on the assessment of electrocardiogram-based safety measurements of the PR and QRS intervals, representing atrioventricular and ventricular conduction, respectively, during drug development.

Factors influencing the decision to ICD implantation in survivors of OHCA and its influence on long term survival

BACKGROUND

Knowledge is insufficient of the long-term benefit of an implantable cardioverter defibrillator (ICD) after out of hospital cardiac arrest (OHCA).

AIM

To describe the use and factors of importance for outcome in relation to ICD use among survivors of ventricular fibrillation (VF).

METHODS

In consecutive patients discharged alive after OHCA in Gothenburg between 1988 and 2008 the long-term prognosis was followed.

RESULTS

In all, there were 5443 OHCAs of which 1489 (27%) were hospitalized alive. Of those, 495 (33%) were discharged alive, of which 390 (79%) had shockable rhythm. The use of ICDs increased, but only 58 of 390 (15%) had an ICD. Among patients who received an ICD, the 2-year mortality was 2%, versus 25% of those who did not (p<0.0001). In follow-up (mean 5.5 years; maximum 10 years), the use of an ICD showed a borderline association with mortality (adjusted hazard ratio 0.49; 95% confidence interval, 024-1.01; p=0.052). Patients who had ICD were younger and had better cerebral function compared with patients without. Predictors for mortality were cerebral function at discharge, age, history of heart failure and myocardial infarction and no coronary angiography during hospitalization.

CONCLUSION

Among survivors of OHCA caused by VT/VF who had ICD during hospitalization only 2% died during the subsequent 2 years. The use of ICDs was low but increasing. Factors of importance for mortality were cerebral function at the time of discharge, age, history of heart failure and myocardial infarction and no coronary angiography during hospitalization.

Sex difference and factors associated with outcome in patients with sustained ventricular arrhythmias

OBJECTIVE

To describe gender differences and factors of importance for outcome in patients referred for sustained ventricular arrhythmias.

RESULTS

Two hundred and fifty three patients took part in the survey, 126 (20 women) had sustained monomorphic ventricular tachycardia (VT) and 127 (31 women) had polymorphic VT/ventricular fibrillation. Ischemic heart disease was less common in women than in men (47 vs. 80%). At discharge, an ICD implant was similarly common in women (33%) and men (29%). One hundred and twenty five (65%) men and 37 (79%) women were alive at follow-up, p =0.08 (median follow-up 53 months). Independent predictors of long-term mortality were: 1) PVT/VF as the presenting arrhythmia, 2) a low ejection fraction, 3) increased QRS duration and 4) diabetes mellitus.

CONCLUSION

The lower proportion of women compared to men being referred for evaluation of sustained ventricular arrhythmias may contribute to the lower number of ICD implants in women. The long-term survival in women and men did not differ significantly.

Testing the Implantable Cardioverter-Defibrillator After Implantation?Is It Necessary?

The results of intraoperative and postoperative predischarge implantable cardioverter-defibrillator (ICD) testing of 211 consecutive patients, starting at 15 J and requiring two successful terminations of induced VT/VF with a relative defibrillation safety margin (DSM) of >10 J, were reviewed. The aim was to define the type of intraoperative response that would make postoperative predischarge testing unnecessary. The intraoperative responses were divided into three types: A, a DSM > or =10 J and an absolute energy level of < or =20 J; B, a DSM of > or =10 J and an absolute energy level of >20 J; and C, a DSM <10 J and an absolute energy level of >20 J. At operation, the responses to defibrillation were A, 88.6%; B, 7.1%; and C, 4.3%. Accepting an A response only would leave 11.4% of the patients for postoperative testing. The positive and negative predictive values for diagnosing a postoperative C response were 0.78 and 0.97, respectively. Similarly, the predictive values for diagnosing a postoperative B or C response were 0.71 and 0.97, respectively. The postoperative testing responses were A, 89.1%; B, 4.3%; and C, 6.6%. In summary, an intraoperative A response was sufficient to make a postoperative defibrillation testing unnecessary, while it was found that intraoperative B and C responders should undergo postoperative testing. Applying these criteria, approximately 90% of the patients could be discharged without any postoperative induction test.

Spectral turbulence and late potentials in the signal-averaged electrocardiograms of patients with monomorphic ventricular tachycardia versus resuscitated ventricular fibrillation

Signal-averaged electrocardiograms (SAECG) were analyzed for late potentials and spectral turbulence in 208 patients with ischemic heart disease with a history of sustained monomorphic ventricular tachycardia (MVT) (n = 62), resuscitation from ventricular fibrillation (VF) (n = 64) or no ventricular tachyarrhythmia (n = 82). Receiver operating characteristic curves were utilized to optimize cut-off values for prediction of MVT and VF. Patients with MVT had a lower ejection fraction (mean = 0.37) than patients with VF (0.44; p = 0.01) and controls (0.48; p < 0.0001). The mean FQRSD in MVT patients (126 ms) was longer than in VF and controls (113 ms; p = 0.005 and 102 ms; p < 0.0001, respectively). The RMS40 was lower in MVT (19 microV) than in VF and controls (29 microV; p = 0.0003 and 28 microV; p < 0.0001, respectively); 81% of the MVT patients were spectral turbulence-positive vs 47% of VF patients and 31% of control patients (p < 0.0001 for both differences). With optimized reference values, FQRSD, TQRSD and ISCSD contributed significantly to the identification of MVT patients and FQRSD to VF patients. The sensitivity of combined time-domain and spectral turbulence analysis was 90% for MVT and 58% for VF, with 63% specificity. MVT patients had a lower ejection fraction and were more often late potential and spectral turbulence positive than VF and control patients. These findings indicate that a large electroanatomic substrate is required in MVT. A long FQRSD was a risk marker for both MVT and VF. Spectral turbulence analysis added independent information, and the combination of time-domain and spectral turbulence analysis was superior to either method alone in identifying the MVT patients. Neither method of analysis, singly nor in combination, performed satisfactorily in identification of VF risk.

The short-term and long-term reproducibility of spectral turbulence and late potential variables of the signal-averaged ECG in a population sample of healthy subjects and the impact of gender, age, and noise

Previous methods for frequency domain analysis of the signal-averaged ECG (SAECG) have had low reproducibility. The reproducibility of time domain late potential analysis and spectral turbulence analysis was evaluated with 2 immediately consecutive SAECG recordings in 121 randomly selected subjects without heart disease (short-term) and also in 47 subjects after 1 month (long-term). A test was late potential positive if 2 or more of 3 variables were outside the reference limits and spectral turbulence positive if the score was 3 or 4. The short-term reproducibility was high for the filtered QRS duration (FQRSD), root mean square amplitude of the last 40 ms (RMS40) and high frequency low amplitude signals less than 40 microV (HFLAS40) of the time domain and total QRS duration (TQRSD), power spectral density of the last 40 ms and the late potential duration of time domain analogous analyses. The Spearman rank order correlation coefficients were 0.89, 0.88, and 0.84 and 0.97, 0.91 and 0.97, respectively. The reproducibility of the spectral score variables varied, and the correlation for the low slice correlation ratio was 0.71, spectral entropy 0.61, interslice correlation mean 0.58, and interslice correlation SD 0.28. A diagnostic inconsistency between 2 tests occurred in 0 (0%) subjects in late potential analysis if FQRSD was required for positivity, and in 7 (6%) otherwise, and in 9 (7%) of spectral turbulence analysis. If the spectral variable mean peaks per slice, with a correlation of 0.89, replaced interslice correlation SD in the spectral score, diagnostic inconsistency occurred in 0 (0%) subjects. The reproducibility seemed higher in women and in younger people but significantly only for interslice correlation subjects mean and HFLAS40. The long-term reproducibility did not differ significantly from short-term for any variable. In conclusion, the reproducibility was high in all time domain and time domain analogous variables. It varied among the spectral turbulence score variables and was very low for interslice correlation SD. The reproducibility of the spectral score improved substantially if this variable was replaced by mean peaks per slice.

Full ventricular capture indicated by the QT interval function

The atrioventricular (AV) interval is critical in dual chamber (DDD) pacing in patients with hypertrophic obstructive cardiomyopathy (HOCM) to obtain full ventricular capture (FVC) with maximal reduction of the left ventricular (LV) outflow gradient and optimal LV diastolic filling. We studied the relationship of FVC, fusion, spontaneous AV conduction, and the QT interval.

METHODS

11 patients with various cardiac diseases and stable AV conduction received a QT sensing Diamond, Vitatron, DDD pacemaker. Software was downloaded into the pacemaker. In the DDD pacing mode, with the QT interval measured from the ventricular pacing stimulus to the end of the T wave, the AV interval was shortened from 400 ms, in 20-ms steps, to 90 ms. At 90 ms the stimulation rate was increased by 30 beats/min and the AV interval was increased stepwise. FVC and fusion was examined on the surface ECG.

RESULTS

At 400 ms interval, spontaneous AV conduction inhibited the pacemaker. Shortening the AV interval resulted in pacing with a short QT interval. Further reduction of the AV interval resulted in a longer QT interval up to a point where the QT interval became stable. This point, the bending point in the plot of measured QT interval versus shortened AV intervals, coincided with the point of FVC. The relation of the QT-AV interval plot and the point of fusion was comparable when lengthening the AV interval at a 30 beats/min faster stimulation rate.

CONCLUSION

The bending point in the QT interval versus AV interval plots showed a good correlation with the FVC and fusion points observed on ECG. The results suggest that automatic discrimination between fusion and full capture using QT interval measurements may be feasible.

Tolerance and effects of almokalant, a new selective Ik blocking agent, on ventricular repolarization and on sino-atrial and atrioventricular nodal function in the heart: a study in healthy, male volunteers utilizing transesophageal atrial stimulation

Almokalant, (4-(3-ethyl(3-propylsulfinyl)propyl)amino)-2-hydroxy-propoxy)- benzonitrile), is a newly developed Ik channel blocker that exhibits pure class III effects. Using a noninvasive approach with transesophageal atrial stimulation (TAS), we wished to identify the dose of almokalant, given as an intravenous bolus infusion, that prolonged ventricular repolarization in the healthy human heart to an extent of potential clinical interest. Furthermore, we defined the electrophysiological effects of this dose on the heart, as well as the pharmacokinetics, safety, and tolerance throughout a wide dosing range. In the titration part, increasing doses were given to identify the dose that produced a reproducible QTend prolongation of approximately 20%. This dose (12.8 mumol) was then given in a placebo-controlled, double-blind, cross-over fashion. In the double-blind part, almokalant significantly prolonged the QTend intervals during sinus rhythm and during TAS at 100 beats/min and increased the effective refractory period of the atria (AERP). There was no alteration in either the cardiac conduction (PQ and QRS), or blood pressure (BP) sinus node function, or the ERP of the atrioventricular (AV) node. Therefore, almokalant exhibited pure class III effects with no signs of beta-blockade or unwanted hemodynamic effects. The plasma concentration-time curve showed a biexponential decrease with a terminal half-life (t1/2) of approximately 3 h. There was a large interindividual variation in the plasma concentration at the end of infusion, Cmax. This variability diminished considerably 60 min after infusion, and the pharmacokinetic characteristics studied appeared to be proportional to the dose. The drug was well tolerated, and the only side effect noted was a brief metallic taste after a dose of 25.6 mumol. Corresponding to high plasma peak values, T-wave morphology changes of short duration were observed, sometimes with the development of pronounced, biphasic T waves.