Scholars@Duke
Zak Loring

Zak Loring

Assistant Professor of Medicine
Medicine, Cardiology

Selected Publications

Casting a Wide (QT) Net to Prevent Torsades de Pointes.

Journal Article JACC Clin Electrophysiol · May 2024 Full text Link to item Cite

Natural history of echocardiographic changes in atrial fibrillation: A case-controlled study of longitudinal remodeling.

Journal Article Heart Rhythm · January 2024 BACKGROUND: Atrial fibrillation (AF) can be a cause and consequence of cardiac remodeling. The natural history of remodeling associated with AF is incompletely described. OBJECTIVE: The purpose of this study was to describe the frequency and timing of AF-a ... Full text Link to item Cite

Electrocardiographic parameters associated with pacemaker induced cardiomyopathy.

Journal Article J Electrocardiol · 2023 BACKGROUND: Chronic right ventricular (RV) pacing can induce left ventricular (LV) dyssynchrony and cause pacemaker induced cardiomyopathy (PiCM). Identifying which patients are at risk for PiCM is limited. METHODS: Patients receiving RV-only permanent pac ... Full text Link to item Cite

Healthcare-seeking behaviour, barriers to care and predictors of symptom improvement among patients with cardiovascular disease in northern Tanzania.

Journal Article Int Health · July 1, 2022 BACKGROUND: Little is known about healthcare-seeking behaviour and barriers to care for cardiovascular disease (CVD) in sub-Saharan Africa. METHODS: Emergency department patients in Tanzania with acute CVD were prospectively enrolled. Questionnaires were a ... Full text Open Access Link to item Cite

Acute echocardiographic and hemodynamic response to his-bundle pacing in patients with first-degree atrioventricular block.

Journal Article Ann Noninvasive Electrocardiol · July 2022 BACKGROUND: Atrial pacing and right ventricular (RV) pacing are both associated with adverse outcomes among patients with first-degree atrioventricular block (1°AVB). His-bundle pacing (HBP) provides physiological activation of the ventricle and may be abl ... Full text Link to item Cite

Is there a mortality benefit of atrial fibrillation ablation?

Journal Article J Cardiovasc Electrophysiol · February 2022 Full text Link to item Cite

Diagnosis-to-ablation time predicts recurrent atrial fibrillation and rehospitalization following catheter ablation.

Journal Article Heart Rhythm O2 · February 2022 BACKGROUND: Wait times for catheter ablation in patients with symptomatic atrial fibrillation (AF) may influence clinical outcomes. OBJECTIVE: This study examined the relationship between the duration from AF diagnosis to ablation, or diagnosis-to-ablation ... Full text Open Access Link to item Cite

The prevalence, management, and thirty-day outcomes of symptomatic atrial fibrillation in a Tanzanian emergency department.

Journal Article Afr J Emerg Med · December 2021 INTRODUCTION: Data describing atrial fibrillation (AF) care in emergency centres (ECs) in sub-Saharan Africa is lacking. We sought to describe the prevalence and outcomes of AF in a Tanzanian EC. METHODS: In a prospective, observational study, adults prese ... Full text Open Access Link to item Cite

The reward of understanding risk in atrial fibrillation.

Journal Article Eur J Prev Cardiol · May 22, 2021 Full text Link to item Cite

Interpretable morphological features for efficient single-lead automatic ventricular ectopy detection.

Journal Article J Electrocardiol · 2021 OBJECTIVE: We designed an automatic, computationally efficient, and interpretable algorithm for detecting ventricular ectopic beats in long-term, single-lead electrocardiogram recordings. METHODS: We built five simple, interpretable, and computationally ef ... Full text Link to item Cite

Predicting the Development of Reduced Left Ventricular Ejection Fraction in Patients With Left Bundle Branch Block.

Journal Article Am J Cardiol · December 15, 2020 Left bundle branch block (LBBB) increases the likelihood of developing reduced left ventricular (LV) ejection fraction (EF) but predicting which patients with LBBB and normal LVEF will develop decreased LVEF remains challenging. Fifty patients with LBBB an ... Full text Link to item Cite

VVI pacing with normal QRS duration and ventricular function: MOST trial findings relevant to leadless pacemakers.

Journal Article Pacing Clin Electrophysiol · December 2020 BACKGROUND: Leadless pacemakers (LPs) provide ventricular pacing without the risks associated with transvenous leads and device pockets. LPs are appealing for patients who need pacing, but do not need defibrillator or cardiac resynchronization therapy. Mos ... Full text Open Access Link to item Cite

Economic Evaluation of Catheter Ablation of Atrial Fibrillation in Patients with Heart Failure With Reduced Ejection Fraction.

Journal Article Circ Cardiovasc Qual Outcomes · December 2020 BACKGROUND: Randomized clinical trials have demonstrated that catheter ablation for atrial fibrillation in patients with heart failure with reduced ejection fraction may improve survival and other cardiovascular outcomes. METHODS: We constructed a decision ... Full text Link to item Cite

Machine learning does not improve upon traditional regression in predicting outcomes in atrial fibrillation: an analysis of the ORBIT-AF and GARFIELD-AF registries.

Conference Europace · November 1, 2020 AIMS: Prediction models for outcomes in atrial fibrillation (AF) are used to guide treatment. While regression models have been the analytic standard for prediction modelling, machine learning (ML) has been promoted as a potentially superior methodology. W ... Full text Link to item Cite

Concomitant changes in ventricular depolarization and repolarization and long-term outcomes of biventricular pacing.

Journal Article Pacing Clin Electrophysiol · November 2020 BACKGROUND: Biventricular (BiV) pacing increases transmural repolarization heterogeneity due to epicardial to endocardial conduction from the left ventricular (LV) lead. However, limited evidence is available on concomitant changes in ventricular depolariz ... Full text Link to item Cite

Procedural Patterns and Safety of Atrial Fibrillation Ablation: Findings From Get With The Guidelines-Atrial Fibrillation.

Journal Article Circ Arrhythm Electrophysiol · September 2020 BACKGROUND: Catheter ablation is an increasingly used treatment for symptomatic atrial fibrillation (AF). However, there are limited prospective, nationwide data on patient selection and procedural characteristics. This study describes patient characterist ... Full text Link to item Cite

Reducing ECG Artifact From Left Ventricular Assist Device Electromagnetic Interference.

Journal Article J Am Heart Assoc · August 18, 2020 Background Left ventricular assist devices (LVADs) generate electromagnetic interference that causes high-frequency noise artifacts on 12-lead ECGs. We describe the causes of this interference and potential solutions to aid ECG interpretation in patients w ... Full text Link to item Cite

Catheter ablation of atrial fibrillation in patients with diabetes mellitus.

Journal Article Heart Rhythm O2 · August 2020 BACKGROUND: Diabetes mellitus (DM) is an independent risk factor for atrial fibrillation (AF). Few studies have compared clinical outcomes after catheter ablation between patients with and those without DM. OBJECTIVE: The purpose of this study was to compa ... Full text Open Access Link to item Cite

The reward of understanding risk in atrial fibrillation.

Journal Article Eur J Prev Cardiol · May 13, 2020 Full text Link to item Cite

Lead one ratio in left bundle branch block predicts poor cardiac resynchronization therapy response.

Journal Article Pacing Clin Electrophysiol · May 2020 BACKGROUND: A low electrocardiogram (ECG) lead one ratio (LOR) of the maximum positive/negative QRS amplitudes is associated with lower left ventricular ejection fraction (LVEF) and worse outcomes in left bundle branch block (LBBB); however, the impact of ... Full text Link to item Cite

Diagnosis-to-Ablation Time and Recurrence of Atrial Fibrillation Following Catheter Ablation: A Systematic Review and Meta-Analysis of Observational Studies.

Journal Article Circ Arrhythm Electrophysiol · April 2020 BACKGROUND: The optimal timing of catheter ablation for atrial fibrillation (AF) in reference to the time of diagnosis is unknown. We sought to assess the impact of the duration between first diagnosis of AF and ablation, or diagnosis-to-ablation time (DAT ... Full text Link to item Cite

Complications involving the subcutaneous implantable cardioverter-defibrillator: Lessons learned from MAUDE.

Journal Article Heart Rhythm · March 2020 BACKGROUND: Reports on the subcutaneous implantable cardioverter-defibrillator (S-ICD) cumulatively demonstrate a low rate of complications, but clinical experience with this technology is limited compared with transvenous devices. OBJECTIVE: The purpose o ... Full text Link to item Cite

Patterns of Emergency Care for Possible Acute Coronary Syndrome Among Patients with Chest Pain or Shortness of Breath at a Tanzanian Referral Hospital.

Journal Article Glob Heart · February 6, 2020 BACKGROUND: Acute coronary syndrome (ACS) is thought to be a rare diagnosis in sub-Saharan Africa, but little is known about diagnostic practices for patients with possible ACS symptoms in the region. OBJECTIVE: To describe current care practices for patie ... Full text Open Access Link to item Cite

Guideline-directed therapies for comorbidities and clinical outcomes among individuals with atrial fibrillation.

Journal Article Am Heart J · January 2020 BACKGROUND: Comorbidities are common in patients with atrial fibrillation (AF) and affect prognosis, yet are often undertreated. However, contemporary rates of use of guideline-directed therapies (GDT) for non-AF comorbidities and their association with ou ... Full text Link to item Cite

Changes in the optimal cardiac resynchronization therapy pacing configuration during physiologic stress.

Journal Article J Electrocardiol · 2020 BACKGROUND: Some patients with ongoing heart failure symptoms after treatment with cardiac resynchronization therapy (CRT) demonstrate QRS prolongation during exercise. We investigated whether the optimal CRT pacing configuration changes during dobutamine ... Full text Link to item Cite

PR Prolongation predicts inadequate resynchronization with biventricular pacing in left bundle branch block.

Journal Article Pacing Clin Electrophysiol · November 2019 BACKGROUND: PR interval prolongation is associated with poor outcome after cardiac resynchronization therapy (CRT) among patients with left bundle branch block (LBBB) but the mechanisms are unknown. We investigated clinical outcomes, electrocardiogram (ECG ... Full text Link to item Cite

Predicting atrial fibrillation recurrence after ablation in patients with heart failure: Validity of the APPLE and CAAP-AF risk scoring systems.

Journal Article Pacing Clin Electrophysiol · November 2019 BACKGROUND: Compared with medical therapy, catheter ablation of atrial fibrillation (AF) in patients with heart failure (HF) improves cardiovascular outcomes. Risk scores (CAAP-AF and APPLE) have been developed to predict the likelihood of AF recurrence af ... Full text Open Access Link to item Cite

Non-invasively quantified changes in left ventricular activation predict outcomes in patients undergoing cardiac resynchronization therapy.

Journal Article J Cardiovasc Electrophysiol · November 2019 BACKGROUND: Changes in left ventricular (LV) activation after cardiac resynchronization therapy (CRT) influence survival but are difficult to quantify noninvasively. METHODS AND RESULTS: We studied 527 CRT patients to assess whether noninvasive quantificat ... Full text Link to item Cite

Machine learning in 'big data': handle with care.

Journal Article Europace · September 1, 2019 Full text Link to item Cite

Low lead one ratio predicts clinical outcomes in left bundle branch block.

Journal Article J Cardiovasc Electrophysiol · May 2019 INTRODUCTION: We evaluated the association between a novel electrocardiographic (ECG) marker of late, rightward electrocardiographic forces (termed the lead one ratio [LOR]), and left ventricular ejection fraction (LVEF), myocardial scar, and clinical outc ... Full text Link to item Cite

Should His Bundle Pacing Be Preferred over Cardiac Resynchronization Therapy Following Atrioventricular Junction Ablation?

Journal Article Cardiol Clin · May 2019 Atrial fibrillation (AF) and heart failure (HF) are associated with high morbidity and mortality, which is particularly detrimental when patients develop rapid ventricular rates (RVR). Atrioventricular junction (AVJ) ablation with pacemaker implantation ha ... Full text Link to item Cite

Impaired Recovery of Left Ventricular Function in Patients With Cardiomyopathy and Left Bundle Branch Block.

Journal Article J Am Coll Cardiol · January 23, 2018 BACKGROUND: Patients with left bundle branch block (LBBB) often respond to cardiac resynchronization therapy (CRT) with left ventricular ejection fraction (LVEF) improvement. Guideline-directed medical therapy (GDMT), not CRT, is first-line therapy for pat ... Full text Link to item Cite

Comparison of Incidence of Left Ventricular Systolic Dysfunction Among Patients With Left Bundle Branch Block Versus Those With Normal QRS Duration.

Journal Article Am J Cardiol · December 1, 2017 We compared the incidence of left ventricular systolic dysfunction (LVSD) among patients with left bundle branch block (LBBB) to a matched cohort of patients with a narrow QRS duration <120 ms (NQRS). We hypothesized patients with preserved ejection fracti ... Full text Link to item Cite

Longer Ambulatory ECG Monitoring Increases Identification of Clinically Significant Ectopy.

Journal Article Pacing Clin Electrophysiol · June 2016 BACKGROUND: Frequent premature ventricular contractions (PVCs) can cause a reversible reduction in systolic function. Most studies use 24-hour ambulatory electrocardiograms (AECGs) to assess PVC burden; however, PVC counts vary across 24-hour periods. We h ... Full text Link to item Cite

A Physician With Thigh Pain.

Journal Article Fed Pract · June 2016 To prevent death, necrotizing soft-tissue infections should be diagnosed quickly and treated with broad-spectrum antibiotics and surgical debridement. ... Link to item Cite

Scar burden assessed by Selvester QRS score predicts prognosis, not CRT clinical benefit in preventing heart failure event and death: A MADIT-CRT sub-study.

Journal Article J Electrocardiol · 2016 BACKGROUND: There is a need for improved selection criteria for Cardiac Resynchronization Therapy (CRT). High myocardial scar burden has been associated with worse outcome in CRT patients. It is, however, unclear whether high scar burden ameliorates CRT cl ... Full text Link to item Cite

The late presenting STEMI: How ECG scores can be used to estimate event time.

Journal Article J Electrocardiol · 2016 INTRODUCTION: Patients presenting with ST elevation myocardial infarction (STEMI) derive significant benefit from timely percutaneous coronary intervention (PCI). Electrocardiogram (ECG) scoring systems can complement history to estimate the infarction age ... Full text Link to item Cite

Comparison of the relation between left ventricular anatomy and QRS duration in patients with cardiomyopathy with versus without left bundle branch block.

Journal Article Am J Cardiol · May 15, 2014 QRS duration (QRSd) is used to diagnose left bundle branch block (LBBB) and is important to determine cardiac resynchronization therapy eligibility. The same QRSd thresholds established decades ago are used for all patients. However, significant interpatie ... Full text Link to item Cite

Improving the assessment of heart toxicity for all new drugs through translational regulatory science.

Journal Article Clin Pharmacol Ther · May 2014 Fourteen drugs have been removed from the market worldwide because they cause torsade de pointes. Most drugs that cause torsade can be identified by assessing whether they block the human ether à gogo related gene (hERG) potassium channel and prolong the Q ... Full text Link to item Cite

Evaluating strict and conventional left bundle branch block criteria using electrocardiographic simulations.

Journal Article Europace · December 2013 AIMS: Left bundle branch block (LBBB) is a critical predictor of patient benefit from cardiac resynchronization therapy (CRT), but recent studies suggest that one-third of patients diagnosed with LBBB by conventional electrocardiographic (ECG) criteria may ... Full text Link to item Cite

Right, but not left, bundle branch block is associated with large anteroseptal scar.

Journal Article J Am Coll Cardiol · September 10, 2013 OBJECTIVES: This study sought to test the hypothesis that right bundle branch block (RBBB) patients have larger scar size than left bundle branch block (LBBB) patients do. BACKGROUND: A proximal septal perforating branch of the left anterior descending (LA ... Full text Link to item Cite

ECG quantification of myocardial scar and risk stratification in MADIT-II.

Journal Article Ann Noninvasive Electrocardiol · September 2013 BACKGROUND: Low left ventricular ejection fraction (LVEF) increases risk for both sudden cardiac death (SCD) and for heart failure (HF) death; however, implantable cardioverter-defibrillators (ICDs) reduce the incidence of SCD, not HF death. Distinguishing ... Full text Link to item Cite

Left bundle-branch block: the relationship between electrocardiogram electrical activation and echocardiography mechanical contraction.

Journal Article Am Heart J · August 2013 BACKGROUND: The relationship between myocardial electrical activation by electrocardiogram (ECG) and mechanical contraction by echocardiography in left bundle-branch block (LBBB) has never been clearly demonstrated. New strict criteria for LBBB based on a ... Full text Link to item Cite

Left bundle branch block predicts better survival in women than men receiving cardiac resynchronization therapy: long-term follow-up of ∼ 145,000 patients.

Journal Article JACC Heart Fail · June 2013 OBJECTIVES: The goal of this study was to test the hypothesis that in recipients of cardiac resynchronization therapy defibrillators (CRT-D), conventional left bundle branch block (LBBB) diagnosis predicts better survival in women than in men. BACKGROUND: ... Full text Link to item Cite

Left ventricular mechanical dyssynchrony by cardiac magnetic resonance is greater in patients with strict vs nonstrict electrocardiogram criteria for left bundle-branch block.

Journal Article Am Heart J · June 2013 BACKGROUND: Left bundle-branch block (LBBB) is a marker of increased delay between septal and left ventricular (LV) lateral wall electrical activation and is a predictor of which patients will benefit from cardiac resynchronization therapy. Recent analysis ... Full text Link to item Cite

Cardiac MRI scar patterns differ by sex in an implantable cardioverter-defibrillator and cardiac resynchronization therapy cohort.

Journal Article Heart Rhythm · May 2013 BACKGROUND: Recent meta-analyses suggest that the effectiveness of cardiac devices may differ between genders. Compared to men, women may not benefit as much from implantable cardioverter-defibrillators (ICDs), yet benefit more from cardiac resynchronizati ... Full text Link to item Cite

Localization of myocardial scar in patients with cardiomyopathy and left bundle branch block using electrocardiographic Selvester QRS scoring.

Journal Article J Electrocardiol · 2013 INTRODUCTION: Outcome of cardiac resynchronization therapy is severely worsened by myocardial scar at the left ventricular (LV) pacing site. We aimed to describe the diagnostic performance of electrocardiographic (ECG) criteria based on the Selvester QRS s ... Full text Link to item Cite

The predictive value of an ECG-estimated Acute Ischemia Index for prognosis of myocardial salvage and infarct healing 3months following inferior ST-elevated myocardial infarction.

Journal Article J Electrocardiol · 2013 BACKGROUND AND PURPOSE: Identification of prognostic markers can be used to stratify patients in the acute phase of ST-elevated myocardial infarction (STEMI) according to their potential to retain viable myocardium after reperfusion. The percentage of the ... Full text Link to item Cite

Modeling vectorcardiograms based on left ventricle papillary muscle position.

Journal Article J Electrocardiol · 2011 BACKGROUND: Vectorcardiographic QRS loops illustrate the electrical activation of the left ventricle (LV) in 3-dimensional space; however, the individual variability in these loops is not well understood. The left bundle-branch fan distributes the initial ... Full text Link to item Cite

A detailed guide for quantification of myocardial scar with the Selvester QRS score in the presence of electrocardiogram confounders.

Journal Article J Electrocardiol · 2011 The Selvester QRS score translates subtle changes in ventricular depolarization measured by the electrocardiogram into information about myocardial scar location and size. This estimated scar has been shown to have a high degree of correlation with autopsy ... Full text Link to item Cite

Spartin activates atrophin-1-interacting protein 4 (AIP4) E3 ubiquitin ligase and promotes ubiquitination of adipophilin on lipid droplets.

Journal Article BMC Biol · May 26, 2010 BACKGROUND: Spartin protein is involved in degradation of epidermal growth factor receptor and turnover of lipid droplets and a lack of expression of this protein is responsible for hereditary spastic paraplegia type 20 (SPG20). Spartin is a multifunctiona ... Full text Link to item Cite