Electrical wavefront fusion in heart failure patients with left bundle branch block and cardiac resynchronization therapy: Implications for optimization.

BACKGROUND: Novel metrics of electrical dyssynchrony based on multi-electrode mapping and ECG-based markers of fusion are better predictors of cardiac resynchronization therapy (CRT) response than QRS duration. OBJECTIVE: To describe a new methodology for measuring electrical synchrony based on wavefront fusion and electrocardiographic cancellation in patients with CRT and its potential for CRT optimization. METHODS: Patients with left bundle branch block (LBBB) type conduction and CRT (n = 84) were studied at multiple device settings using an ECG belt (53 anterior and posterior electrodes). The area between combinations of anterior and posterior curves (AUC) was calculated and cardiac resynchronization index (CRI) defined as percent change in AUC compared to LBBB. RESULTS: In 14 patients with complete heart block or atrial fibrillation, CRI at optimal ventriculo-ventricular delay (VVD) (40 ± 19 ms) was significantly higher than with simultaneous biventricular pacing (BiVp) (90 ± 8.6% vs. 54.2 ± 24.2%, p < 0.001). In all 70 patients paced LV-only, LV-paced wavefront was ahead of native wavefront at short atrio-ventricular delay (AVD) and CRI increased with increase in AVD, peaked, and then decreased. Optimal CRI during LV-only pacing was significantly better than optimal CRI with simultaneous BiVp (89.6 ± 8% vs. 64.4 ± 22%, p < 0.001), and occurred at AVD 68 ± 22 ms less than the atrial-RV sensed interval. With sequential BiVp, best CRI was 83.9 ± 13% (with LV preactivation of 40 ± 20 ms). Best CRI at any setting was markedly better than CRI at standard setting (91.6 ± 7.7% vs. 52.7 ± 23.3, p < 0.001). CONCLUSION: We describe a novel non-invasive investigational tool that quantifies wavefront fusion and electrical dyssynchrony, and may allow for individualized CRT optimization.

Body surface activation mapping of electrical dyssynchrony in cardiac resynchronization therapy patients: Potential for optimization.

BACKGROUND: Electrical synchronization is likely improved by cardiac resynchronization therapy (CRT), but is difficult to quantify with 12-lead ECG. We aimed to quantify changes in electrical synchrony and potential for optimization with CRT using a body-surface activation mapping (BSAM) system. METHODS: Standard deviation of activation times (SDAT) was calculated in 94 patients using BSAM at baseline CRT (CRTbl), native, and different CRT configurations. RESULTS: SDAT decreased 20% from native to CRTbl (p<0.01) and an additional 26% (p<0.01) at optimal CRT (CRTopt), the minimal SDAT setting. Patients with LBBB and patients with QRS duration ≥150ms had higher native SDAT and greater decrease with CRTbl (p<0.01); however, the improvement from CRTbl to CRTopt was similar in all four groups (range: 24-28%). CRTopt was achieved with biventricular pacing in 52% and LV-only pacing in 44%. We propose that improved wavefront fusion demonstrated by BSAMs contributed substantially to the improved electrical synchrony. CONCLUSION: Optimization potential is similar regardless of pre-CRT QRS morphology or duration. BSAM could possibly improve CRT response by individualizing device programming to minimize electrical dyssynchrony.

On the underutilization of cardiac resynchronization therapy.

Cardiac resynchronization therapy (CRT) is an exciting therapy that can treat patients with systolic heart failure and left ventricular dysfunction who have a wide QRS complex. Indications for its use have been refined and expanded based on recent clinical data and guidelines, yet the rate of new CRT implants in the United States has not changed much over the past 8 years. Many patients receiving implantable cardioverter-defibrillators can benefit from, but are not receiving, appropriately-indicated CRT devices. We summarize data on CRT use, discuss reasons for probable underutilization, and provide recommendations for augmenting proper and effective use of this highly beneficial therapy.

Comparison of cardiac resynchronization therapy outcomes in patients with New York Heart Association functional class I/II versus III/IV heart failure.

BACKGROUND: Several randomized trials have shown that cardiac resynchronization therapy (CRT) benefits New York Heart Association (NYHA) functional class I/II heart failure (HF) patients, but it is unknown if similar outcomes occur in the real-world. METHODS AND RESULTS: All patients receiving CRT between 2003 and 2008 with ejection fraction (EF) ≤35% and QRS duration ≥120 ms were included. Outcomes assessed were subjective clinical response, echocardiographic response, and survival free of cardiovascular (CV) hospitalization. Baseline demographics in functional class I/II (n = 155) and functional class III/IV (n = 512) were similar, except for differences in age and several comorbidities. Clinical response was similar in both groups. The functional class I/II group had a greater decrease in left ventricular (LV) end-diastolic dimension (P = .031), and trended toward greater improvements in LV end-systolic dimension (P = .056) and EF (P = .059). The functional class I/II group had a better 5-year survival rate (79 vs 54%; P < .0001) and survival free of CV hospitalization (45% vs 26%; P < .0001). CONCLUSIONS: In this real-world clinical scenario, NYHA functional class I/II CRT patients improved clinical status, and LV function and size as good as or better than those in NYHA functional class III/IV patients. These observations provide further support for the use of CRT in patients with mild symptoms of HF.

Cardiac resynchronization therapy in the real world: comparison with the COMPANION study.

BACKGROUND: Several clinical trials have confirmed that cardiac resynchronization therapy (CRT) improves outcomes in well defined patient populations. It is uncertain, however, whether outcomes are similar in real-world clinical settings. This study compared outcomes after CRT with defibrillator (CRT-D) in a large real-world private-practice cardiology setting with those in the COMPANION multicenter trial. METHODS AND RESULTS: A total of 429 consecutive patients who received CRT-D for standard indications (group 1) were retrospectively compared with the 595 patients (group 3) in the COMPANION CRT-D cohort regarding survival and survival free of cardiovascular (CV) hospitalization. A subgroup of the group 1 patients who met the COMPANION entrance criteria (group 2) was also compared with the COMPANION cohort (group 3) both with and without propensity-matching statistical analysis. Survival and survival free of CV hospitalization was better in group 1 than in group 3. Survival in group 2 with and without propensity matching was similar to group 3. However, survival free of CV hospitalization was better in the real-world patients (group 2) even after adjustment for differences in baseline characteristics. CONCLUSIONS: Survival and CV hospitalization outcomes in a real-world clinical setting are as good as, or better than, those demonstrated in the COMPANION research trial.

Pacemaker optimization in nonresponders to cardiac resynchronization therapy: left ventricular pacing as an available option.

BACKGROUND: Echocardiographic (ECHO)-guided pacemaker optimization (PMO) in cardiac resynchronization therapy (CRT) nonresponders acutely improves left ventricular (LV) function. However, the chronic results of LV pacing in this group are less understood. METHODS: We retrospectively studied 28 CRT nonresponders optimized based on ECHO to LV pacing and compared them to 28 age- and gender-matched patients optimized to biventricular (BiV) pacing. ECHOs with tissue Doppler imaging assessed LV hemodynamics before, immediately after, and 29 ± 16 months after PMO. Also, 56 age- and gender-matched CRT responders were included for comparison of clinical outcomes. RESULTS: PMO resulted in acute improvements in longitudinal LV systolic function and several measures of dyssynchrony, with greater improvements in the LV paced group. Chronic improvements in ejection fraction (EF) (3.2 ± 7.7%), and left ventricle end-systolic volume (LVESV) (-11 ± 36 mL) and one dyssynchrony measure were seen in the combined group. Chronically, both LV and BiV paced patients improved some measures of systolic function and dyssynchrony although response varied between the groups. Survival at 3.5 years was similar (P = 0.973) between the PMO (58%) and nonoptimized groups (58%) but survival free of cardiovascular hospitalization was significantly (P = 0.037) better in the nonoptimized group. CONCLUSIONS: CRT nonresponders undergoing PMO to either LV or BiV pacing have acute improvements in longitudinal systolic function and some measures of dyssynchrony. Some benefits are sustained chronically, with improvements in EF, LVESV, and dyssynchrony. A strategy of ECHO-guided PMO results in survival for CRT nonresponders similar to that of CRT patients not referred for PMO.

Twelve-Lead ECG Optimization of Cardiac Resynchronization Therapy in Patients With and Without Delayed Enhancement on Cardiac Magnetic Resonance Imaging.

Background Delayed enhancement ( DE ) on magnetic resonance imaging is associated with ventricular arrhythmias, adverse events, and worse left ventricular mechanics. We investigated the impact of DE on cardiac resynchronization therapy ( CRT ) outcomes and the effect of CRT optimization. Methods and Results We studied 130 patients with ejection fraction ( EF ) ≤40% and QRS ≥120 ms, contrast cardiac magnetic resonance imaging, and both pre- and 1-year post- CRT echocardiograms. Sixty-three (48%) patients did not have routine optimization of CRT . The remaining patients were optimized for wavefront fusion by 12-lead ECG . The primary end point in this study was change in EF following CRT . To investigate the association between electrical dyssynchrony and EF outcomes, the standard deviation of activation times from body-surface mapping was calculated during native conduction and selected device settings in 52 of the optimized patients. Patients had no DE (n=45), midwall septal stripe (n=30), or scar (n=55). Patients without DE had better ∆ EF (13±10 versus 4±10 units; P<0.01). Optimized patients had greater ∆ EF in midwall stripe (2±9 versus 12±12 units; P=0.01) and scar (0±7 versus 5±10; P=0.04) groups, but not in the no- DE group. Patients without DE had greater native standard deviation of activation times ( P=0.03) and greater ∆standard deviation of activation times with standard programming ( P=0.01). Device optimization reduced standard deviation of activation times only in patients with DE ( P<0.01). Conclusions DE on magnetic resonance imaging is associated with worse EF outcomes following CRT . Device optimization is associated with improved EF and reduced electrical dyssynchrony in patients with DE .

Changes in electrical dyssynchrony by body surface mapping predict left ventricular remodeling in patients with cardiac resynchronization therapy.

BACKGROUND: Electrical activation is important in cardiac resynchronization therapy (CRT) response. Standard electrocardiographic analysis may not accurately reflect the heterogeneity of electrical activation. OBJECTIVE: We compared changes in left ventricular size and function after CRT to native electrical dyssynchrony and its change during pacing. METHODS: Body surface isochronal maps using 53 anterior and posterior electrodes as well as 12-lead electrocardiograms were acquired after CRT in 66 consecutive patients. Electrical dyssynchrony was quantified using standard deviation of activation times (SDAT). Ejection fraction (EF) and left ventricular end-systolic volume (LVESV) were measured before CRT and at 6 months. Multiple regression evaluated predictors of response. RESULTS: ∆LVESV correlated with ∆SDAT (P = .007), but not with ∆QRS duration (P = .092). Patients with SDAT ≥35 ms had greater increase in EF (13 ± 8 units vs 4 ± 9 units; P < .001) and LVESV (-34% ± 28% vs -13% ± 29%; P = .005). Patients with ≥10% improvement in SDAT had greater ∆EF (11 ± 9 units vs 4 ± 9 units; P = .010) and ∆LVESV (-33% ± 26% vs -6% ± 34%; P = .001). SDAT ≥35 ms predicted ∆EF, while ∆SDAT, sex, and left bundle branch block predicted ∆LVESV. In 34 patients without class I indication for CRT, SDAT ≥35 ms (P = .015) and ∆SDAT ≥10% (P = .032) were the only predictors of ∆EF. CONCLUSION: Body surface mapping of SDAT and its changes predicted CRT response better than did QRS duration. Body surface mapping may potentially improve selection or optimization of CRT patients.

Left ventricular-only pacing in heart failure patients with normal atrioventricular conduction improves global function and left ventricular regional mechanics compared with biventricular pacing: an adaptive cardiac resynchronization therapy sub-study.

AIMS: Right ventricular (RV) pacing can impair left ventricular (LV) function. When timed with native RV activation, LV-only pacing may cause greater improvements in LV function than biventricular pacing. This study compared the chronic effects of cardiac resynchronization therapy (CRT) on LV mechanics between biventricular pacing and LV-only pacing in patients with normal atrioventricular (AV) conduction. METHODS AND RESULTS: The Adaptive CRT (aCRT) algorithm provides LV-only pacing timed with native RV activation when the AV interval is normal (≤200 ms during sinus rhythm). We studied patients from the aCRT trial with normal AV conduction at their baseline visit and compared changes in cardiac function after 12 months of treatment with conventional biventricular or mostly (≥80%) LV-only pacing. Speckle tracking echocardiography was used to assess LV myocardial strain before and after treatment. Despite similar improvements in Packer's clinical composite scores and LV volumes, LV-only paced patients (n = 70) had a greater improvement in LV ejection fraction (8.5 ± 11.3% vs. 5.5 ± 10.3%, P = 0.038) and global LV radial strain (6.3 ± 8.6% vs. 4.0 ± 10.1%, P = 0.046) than those randomized to biventricular pacing (n = 91). Strain was improved to a greater extent near the RV pacing lead, in septal and apical regions (P < 0.05 for both regions), in patients receiving LV-only pacing. CONCLUSION: In heart failure patients with normal AV conduction, LV-only pacing timed with native RV activation may result in greater improvements in LV ejection fraction and myocardial strain compared with biventricular pacing due to better apical and septal function.

Body surface mapping using an ECG belt to characterize electrical heterogeneity for different left ventricular pacing sites during cardiac resynchronization: Relationship with acute hemodynamic improvement.

BACKGROUND: Electrical heterogeneity (EH) during cardiac resynchronization therapy may vary with different left ventricular (LV) pacing sites. OBJECTIVE: The purpose of this study was to evaluate the relationship between such changes and acute hemodynamic response (AHR). METHODS: Two EH metrics-standard deviation of activation times and mean left thorax activation times-were computed from isochronal maps based on 53-electrode body surface mapping during baseline AAI pacing and biventricular (BiV) pacing from different pacing sites in coronary veins in 40 cardiac resynchronization therapy-indicated patients. AHR at different sites was evaluated by invasive measurement of LV-dp/dtmax at baseline and BiV pacing, along with right ventricular (RV)-LV sensing delays and QRS duration. RESULTS: The site with the greatest combined reduction in standard deviation of activation times and left thorax activation times from baseline to BiV pacing was hemodynamically optimal (defined by AHR equal to, or within 5% of, the largest dp/dt response) in 35 of 40 patients (88%). Sites with the longest RV-LV and narrowest paced QRS were hemodynamically optimal in 26 of 40 patients (65%) and 28 of 40 patients (70%), respectively. EH metrics from isochronal maps had much better accuracy (sensitivity 90%, specificity 80%) for identifying hemodynamically responsive sites (∆LV dp/dtmax ≥10%) compared with RV-LV delay (69%, 85%) or paced QRS reduction (52%, 76%). Multivariate prediction model based on EH metrics showed significant correlation (R2 = 0.53, P <.001) between predicted and measured AHR. CONCLUSION: Changes in EH from baseline to BiV pacing more accurately identified hemodynamically optimal sites than RV-LV delays or paced QRS shortening. Optimization of LV lead location by minimizing EH during BiV pacing, based on body surface mapping, may improve CRT response.

Annual impact of scribes on physician productivity and revenue in a cardiology clinic.

OBJECTIVE: Scribes are increasingly being used in clinics to assist physicians with documentation during patient care. The annual effect of scribes in a real-world clinic on physician productivity and revenue has not been evaluated. METHODS: We performed a retrospective study comparing the productivity during routine clinic visits of ten cardiologists using scribes vs 15 cardiologists without scribes. We tracked patients per hour and patients per year seen per physician. Average direct revenue (clinic visit) and downstream revenue (cardiovascular revenue in the 2 months following a clinic visit) were measured in 486 patients and used to calculate annual revenue generated as a result of increased productivity. RESULTS: Physicians with scribes saw 955 new and 4,830 follow-up patients vs 1,318 new and 7,150 follow-up patients seen by physicians without scribes. Physicians with scribes saw 9.6% more patients per hour (2.50±0.27 vs 2.28±0.15, P<0.001). This improved productivity resulted in 84 additional new and 423 additional follow-up patients seen, 3,029 additional work relative value units (wRVUs) generated, and an increased cardiovascular revenue of $1,348,437. Physicians with scribes also generated an additional revenue of $24,257 by producing clinic notes that were coded at a higher level. Total additional revenue generated was $1,372,694 at a cost of $98,588 for the scribes. CONCLUSION: Physician productivity in a cardiology clinic was ∼10% higher for physicians using scribes. This improved productivity resulted in 84 additional new and 423 additional follow-up patients seen in 1 year. The use of scribes resulted in the generation of 3,029 additional wRVUs and an additional annual revenue of $1,372,694 at a cost of $98,588.

Long-Term Echocardiographic Response to Cardiac Resynchronization Therapy in Initial Nonresponders.

OBJECTIVES: The aim of this study was to investigate the frequency and clinical implications of a delayed echocardiographic response to cardiac resynchronization therapy (CRT). BACKGROUND: Long-term prognosis for CRT patients is routinely based on the assessment of echocardiograms after 6 to 12 months of therapy. Some patients, however, may require a longer period of therapy before echocardiographic improvements are detectable. METHODS: This observational study included all patients with heart failure (HF) receiving a CRT device at a single center from 2003 to 2011. Eligible patients met current indications and had technically adequate echocardiograms from before implantation, approximately 1 year after implantation (mid-term), and ≥3 years after implantation (long-term). A positive echocardiographic response to CRT was defined as a reduction in left ventricular end-systolic volume ≥15%. All-cause mortality was compared for patients in 3 response groups: mid-term responders, long-term responders, and nonresponders. RESULTS: During this study, 294 patients met the study criteria. Of the 120 patients who were nonresponders after 1 year, 52 (43%) experienced a delayed positive response. Delayed, long-term responders had mortality and hospitalization rates similar to mid-term responders and significantly lower than nonresponders. CONCLUSIONS: Among patients surviving at least 3 years after implantation of a CRT device and with echocardiographic follow-up, a significant portion of nonresponders after 1 year of CRT experience a delayed echocardiographic response after a longer period of time. Survival and hospitalization rates were similar for all echocardiographic responders, regardless of the time at which the response occurred.

Mechanical dyssynchrony is additive to ECG criteria and independently associated with reverse remodelling and clinical response to cardiac resynchronisation therapy in patients with advanced heart failure.

BACKGROUND: QRS duration and morphology are known established predictors of cardiac resynchronisation therapy (CRT) response, whereas mechanical dyssynchrony is not. Our aim was to determine if mechanical dyssynchrony provides independent prognostic information on CRT response. METHODS: We studied 369 consecutive patients with heart failure (HF) with low ejection fraction (EF) and widened QRS receiving CRT. Radial dyssynchrony (septal-posterior radial peak strain delay ≥130 ms by speckle tracking) assessment was possible in 318 patients (86%). Associations with left ventricular end-systolic volume (LVESV) changes were examined using linear regression, and clinical outcomes analysed using Cox regression adjusted for multiple established outcome correlates. RESULTS: Patients with radial dyssynchrony before CRT (64%) had greater improvements in EF (8.8±9.4 vs 6.1±9.7 units, p=0.04) and LVESV (-30±41 vs -10±30 mL, p<0.01). Radial dyssynchrony was independently associated with reduction in LVESV (regression coefficient -10.5 mL, 95% CI -20.5 to -0.5, p=0.040) as was left bundle-branch block (-17.7 mL, -27.6 to -7.7, p=0.001). Patients with radial dyssynchrony had a 46% lower incidence of death, transplant or implantation of a left ventricular assist device (adjusted HR 0.54, 95% CI 0.31 to 0.92, p=0.02) and a 39% lower incidence of death or HF hospitalisation (0.61, 0.40 to 0.93, p=0.02) over 2 years. CONCLUSIONS: Radial dyssynchrony was associated with significant improvements in LVESV and clinical outcomes following CRT and is independent of QRS duration or morphology, and additive to current ECG selection criteria to predict response to CRT.

Echocardiographic and clinical response to cardiac resynchronization therapy in heart failure patients with and without previous right ventricular pacing.

AIMS: Right ventricular pacing (RVp) results in an electrocardiographic left bundle branch block pattern and can lead to heart failure. This study aimed to evaluate echocardiographic and clinical outcomes of heart failure patients with RVp upgraded to cardiac resynchronization therapy (CRT), as they are frequently excluded from multicentre studies. METHODS AND RESULTS: This observational study assessed 655 consecutive patients with QRS ≥120 ms and left ventricular ejection fraction ≤35%. There were 465 patients without significant previous RVp and 190 with RVp >40%. Echocardiograms were analysed pre-CRT and ∼ 1 year post-CRT. Death and heart failure hospitalizations were analysed using Cox regression, adjusted for baseline characteristics. The RVp patients had smaller end-systolic volume (P = 0.002), were older (P < 0.001), and had more atrial fibrillation (P < 0.001) pre-CRT. Ejection fraction and proportion of ischaemic aetiology were similar. One year following CRT implantation the ejection fraction response was greater in the RVp group (8.3 ± 9 vs. 5.8 ± 9 units, P = 0.005). The RVp patients had an adjusted 33% lower risk of death or heart failure hospitalization [hazard ratio (HR) 0.67 95% confidence interval (CI) 0.51-0.89, P = 0.005], while tending to have an adjusted lower risk of death (HR 0.73 95% CI 0.53-1.01, P = 0.055). CONCLUSION: Despite similar ejection fraction pre-CRT, patients upgraded to CRT with previous RVp have smaller end-systolic volume and respond to CRT at least as well as, if not better than, other wide QRS heart failure patients. A greater improvement in ejection fraction and a lower risk of death or heart failure hospitalization when adjusted for baseline characteristics were seen in those with previous RVp.

Evaluation of traditional and novel measures of cardiac function to detect anthracycline-induced cardiotoxicity in survivors of childhood cancer.

PURPOSE: Cardiovascular disease is the leading noncancer cause of death among survivors of childhood cancer. Ejection fraction (EF) and fractional shortening (FS) are common echocardiographic measures of cardiac function, but newer imaging modalities may provide additional information about preclinical disease. This study aimed to evaluate these modalities in detection of anthracycline-induced cardiac toxicity. METHODS: We compared mean radial displacement, EF, and FS among 17 adult survivors of childhood cancer exposed to ≥ 300 mg/m(2) of anthracyclines to 17 age- and sex-matched healthy controls. Survivors with a history of cardiac-directed radiation, diabetes, or heart disease were excluded. RESULTS: Survivors (35% male), mostly with history of treatment for a solid tumor, had a median age at diagnosis of 15 years (1-20) and 27 years (18-50) at evaluation. Median anthracycline exposure was 440 (range 300-645) mg/m(2). FS (35.5 vs. 39.6%, p < 0.01) and radial displacement (5.6 vs. 6.7 mm, p = 0.02) were significantly lower in survivors compared to controls, respectively. Although the mean EF was lower in survivors versus controls (55.4 vs. 59.7%), it was not statistically significant (p = 0.057). All echocardiographic measures were inversely associated with anthracycline dose, though radial displacement was no longer significantly correlated with anthracycline dose after controlling for survival time (p = 0.07), while EF remained correlated (p = 0.003). IMPLICATIONS FOR CANCER SURVIVORS: Radial displacement, EF, and FS are lower in childhood cancer survivors compared to controls. In this study, radial displacement added no new information beyond the traditional measures, but clinical utility remains undetermined and requires further longitudinal study.

Impact of scribes on patient interaction, productivity, and revenue in a cardiology clinic: a prospective study.

OBJECTIVE: Scribes have been used in the emergency department to improve physician productivity and patient interaction. There are no controlled, prospective studies of scribe use in the clinic setting. METHODS: A prospective controlled study compared standard visits (20 minute follow-up and 40 minute new patient) to a scribe system (15 minute follow-up and 30 minute new patient) in a cardiology clinic. Physician productivity, patient satisfaction, physician-patient interaction, and revenue were measured. RESULTS: Four physicians saw 129 patients using standard care and 210 patients with scribes during 65 clinic hours each. Patients seen per hour increased (P < 0.001) from 2.2 ± 0.3 to 3.5 ± 0.4 (59% increase) and work relative value units (wRVU) per hour increased (P < 0.001) from 3.5 ± 1.3 to 5.5 ± 1.3 (57% increase). Patient satisfaction was high at baseline and unchanged with scribes. In a substudy, direct patient contact time was lower (9.1 ± 2.0 versus 12.9 ± 3.4 minutes; P < 0.01) for scribe visits, but time of patient interaction (without computer) was greater (6.7 ± 2.1 versus 1.5 ± 1.9 minutes; P < 0.01). Subjective assessment of physician-patient interaction (1-10) was higher (P < 0.01) on scribe visits (9.1 ± 0.9 versus 7.9 ± 1.1). Direct and indirect (downstream) revenue per patient seen was $142 and $2,398, with $205,740 additional revenue generated from the 81 additional patients seen with scribes. CONCLUSION: Using scribes in a cardiology clinic is feasible, produces improvements in physician-patient interaction, and results in large increases in physician productivity and system cardiovascular revenue.

Right ventricular pacing, mechanical dyssynchrony, and heart failure.

Cardiac pacing is a common treatment option for patients with sick sinus syndrome or atrioventricular block, with the ventricular pacing lead often secured in the convenient right ventricular (RV) apical location. While RV pacing reduces symptoms and limitations associated with heart block, it may have detrimental effects on cardiac structure and function, leading to heart failure (HF) in some patients. RV pacing creates electrical dyssynchrony similar to a left-bundle branch block, with conduction occurring cell-by-cell rather than through the His-Purkinje network. Studies have shown that impairment of myocardial metabolism, structure, and function related to RV pacing occurs regionally (most prominently near the pacing site) and globally, within the left ventricle. Strategies being studied to prevent or treat pacing-induced intraventricular mechanical dyssynchrony and HF include: initial biventricular rather than RV pacing in selected patients, programming to avoid or minimize RV pacing, use of alternate (non-apical) RV pacing sites, echocardiographic screening for development of pacing-induced dyssynchrony and HF, and upgrade to biventricular pacing.