Jugular Approach for the Transcatheter Pacemaker Implant　- Better Access for Smaller Hearts?

BACKGROUND: The Micra leadless pacemaker was developed to fit inside the right ventricle, thereby reducing overall complications by 48% compared with a historical control group. The current labeling restricts implants to the femoral approach. In this article we used 3-dimensional computer models of human hearts to demonstrate why implants can be difficult in small patients and how using the jugular approach reduces these difficulties.Methods and Results: Cardiac computed tomography scans were made of 45 pacemaker patients, 26 in the US and 19 from a single center in Japan. Dimensional measurements were taken in all 45 hearts, and these dimensions were compared between patient cohorts and between the Micra delivery tool dimension and patient heart dimensions. Hearts were smaller among patients in the Japanese than US cohort. In addition, the tool dimension exceeded heart dimensions in a larger percentage of hearts from Japanese patients. Three dimensions were identified that most likely limit navigating across the tricuspid valve to the right ventricle in smaller hearts and for which the jugular approach improved navigation. CONCLUSIONS: Although the femoral procedure today maintains an excellent safety profile and procedure experience for most global implants, this study provides the rationale as to why the jugular approach may improve the ease of the Micra implant in small hearts, namely by reducing the tortuosity of the navigation across the tricuspid valve.

Visual observation of extraction of a Micra leadless pacemaker from a human cadaver.

INTRODUCTION: In this article we present the extraction of a Micra from a human cadaver implanted 3 years previously with both visual and X-ray imaging taken during the removal. METHODS: A Micra pacemaker was extracted from a human cadaver with endoscopy and fluoroscopy using a Micra delivery tool. Histological analysis was performed on slices from the tissue surrounding the Micra. RESULTS: The fully encapsulated Micra was easily retrieved with a maximum force of 1.9 pounds. CONCLUSIONS: Even though the Micra was implanted almost 3 years previously, the snaring and extraction of the Micra was performed relatively easily and with minimal force required.

Acute effects of biventricular pacing in heart failure patients with a normal ejection fraction and mechanical dyssynchrony.

OBJECTIVES: We tested the acute effects of resynchronization in heart failure patients with a normal (>50%) left ventricular (LV) ejection fraction (HFNEF) and mechanical dyssynchrony. METHODS: Twenty-four HFNEF patients (72 ± 6 years, 5 male) with mechanical dyssynchrony (standard deviation of electromechanical time delay among 12 LV segments >35 ms) were studied with temporary pacing catheters in the right atrium, LV, and right ventricle (RV), and high-fidelity catheters for pressure recording. Using selected atrioventricular (AV) intervals of 60, 90, 120, 150, and 180 ms to optimize transmitral flow during simultaneous biventricular pacing, the RV-LV (VV) interval was then evaluated at RV30, RV15, 0, LV15, LV30, and LV45 (RV or LV indicates which ventricle was paced first, the number indicates by how many ms). RESULTS: During simultaneous pacing, longer AV intervals were associated with improved LV pressure-derivative minimums and increased aortic pressures (p < 0.05 vs. normal sinus rhythm). In the VV interval from RV30 to LV45, there was a graded increase in the aortic velocity time integral and a decrease in dyssynchrony during simultaneous or LV-first pacing (p < 0.05 vs. normal sinus rhythm). CONCLUSIONS: For HFNEF patients with mechanical dyssynchrony, acute simultaneous biventricular or LV-first pacing with longer AV intervals reduced mechanical dyssynchrony and improved diastolic and systolic hemodynamics.

Haemodynamic effects of different basic heart rates in ambulatory heart failure patients treated with cardiac resynchronization therapy.

AIMS: The impact of different basic paced heart rates (pHRs) in patients receiving cardiac resynchronization therapy (CRT) remains largely unknown. The aim of the present study was to investigate the haemodynamic effects of different pHRs (60 or 80 b.p.m.), using an implanted haemodynamic monitor (IHM), during a 2-week period in ambulatory CRT patients. METHODS AND RESULTS: Ten CRT patients received an IHM (Chronicle(®), Medtronic Inc.) to continuously record right ventricular systolic (RVSP) and diastolic (RVDP) pressure, as well as estimated pulmonary artery diastolic pressure (ePAD) during a 2-week period at two basic pHR programming (60 and 80 b.p.m.). Cardiac output (CO) was calculated using a validated IHM algorithm. At the end of each period, 6 min walk test (6MWT), quality of life (QoL), and plasma levels of brain natriuretic peptide (BNP) were also assessed. Pacing at 80 b.p.m. significantly reduced the 2-week average of ePAD compared with 60 b.p.m. (23.4 ± 6.2 vs. 25.1 ± 6.5 mmHg, P = 0.03), whereas CO was increased (4.5 ± 1.3 vs. 4.2 ± 1.4 L/min; P = 0.01). Similarly ePAD, RVSP, and RVDP were significantly lower with a pHR of 80 b.p.m. (P < 0.05). The 6MWT, QoL score, and BNP were not affected by the pHR. CONCLUSION: In CRT patients, a basic pHR of 80 b.p.m. compared with 60 b.p.m. reduces filling pressures and increases CO during a 2-week period of ambulatory living. This suggests that increasing the basic pHR may be considered to achieve short-term haemodynamic improvement. The long-term effects of differential pHR programming remain to be established.

Impact of ventricular dyssynchrony on postexercise accommodation of systolic myocardial motion in hypertensive patients with heart failure and a normal ejection fraction: a tissue-Doppler echocardiography study.

BACKGROUND: We hypothesized left ventricular (LV) dyssynchrony would affect postexercise accommodation of regional myocardial motion in patients with heart failure and a normal ejection fraction (HFNEF). METHODS AND RESULTS: Tissue-Doppler echocardiography was studied in 100 hypertensive patients with LV ejection fraction >50%. Among them, 70 HFNEF patients were classified into the systolic dyssynchrony (Dys: >65 ms difference of electromechanical delay between septal and lateral segments) (43 patients) and nondyssynchrony (Ndys: 27 patients) groups, and the other 30 patients were as the control (Ctrl). The systolic myocardial velocities (Sm) of 6-basal LV segments at baseline and after exercise were analyzed. When compared with the Ctrl group, the baseline lower mean Sm of 6 LV segments in the Ndys group could increase to a similar postexercise level as that in the Ctrl group, whereas that in the Dys group remained lower after exercise (7.8 ± 1.3 versus Ndys: 8.6 ± 1.5 and Ctrl: 8.9 ± 1.2 cm/s, P < .05, respectively). This is mainly due to a much higher percentage increase of lateral Sm after exercise in the Ndys group (Ndys: 49 versus Dys: 29%, P < .05). CONCLUSIONS: Dyssynchrony-related regional myocardial contractile abnormality after exercise in HFNEF patients suggested the detrimental impact of electromechanical uncoupling on HF symptoms.

Cardiac resynchronization therapy may benefit patients with left ventricular ejection fraction >35%: a PROSPECT trial substudy.

AIMS: Cardiac resynchronization therapy (CRT) is currently limited to those with left ventricular ejection fraction (LVEF) < or =35%. To evaluate whether patients with LVEF >35% might benefit from CRT, we performed a retrospective analysis of the predictors of response to CRT (PROSPECT) database. METHODS AND RESULTS: PROSPECT was a prospective, multicentre study that enrolled CRT patients based on enrolling centre-evaluated LVEF <35%, but all echocardiograms were subsequently analysed by a core laboratory. Patients with core laboratory-measured LVEF >35% (OVER35) were compared with those whose LVEF was <35% (UNDER35). Clinical composite score (CCS) and change in LV end systolic volume (LVESV) were analysed from baseline to 6-month follow-up. Of 361 patients, 86 (24%) had LVEF >35%. At entry, OVER35 had smaller LV volumes, shorter QRS duration, shorter 6-min walk distance, and were more likely to have ischaemic aetiology than UNDER35. Outcomes were comparable between the groups, with 62.8% of OVER35 improved in CCS (70.2% in UNDER35) and 50.8% of OVER35 improved in LVESV (57.8% in UNDER35). CONCLUSION: Patients with LVEF >35%, New York heart association functional Class III-IV status, and QRS >130 ms appear to derive clinical and structural benefit from CRT. As CRT may offer a valuable option for these patients, this hypothesis should be formally tested in a prospective, randomized multicentre trial.

Shorter AV delays provide improved echocardiographic hemodynamics during exercise in patients receiving cardiac resynchronization therapy.

BACKGROUND: Although atrial ventricular (AV) intervals are often optimized at rest in patients receiving cardiac resynchronization therapy (CRT), there are limited data on the impact of exercise on optimal AV interval. METHODS: In 15 patients with CRT, AV intervals were serially programmed while patients were supine and at rest, and during exercise with heart rates that averaged 20 and 40 beats per minute above their resting rates. Echocardiographic Doppler images were acquired at each programmed AV interval and each rate. Three independent echocardiographic criteria were retrospectively used to determine each patient's optimal AV interval as a function of exercise-induced increased heart rates: the duration of left ventricular filling, stroke volume, and a clinical assessment of left ventricular function. RESULTS: A negative correlation between the optimal AV interval and heart rate was observed across all patients using all three independent criterion: the maximum left ventricular filling time (slope =-0.77, intercept = 151.9, r = 0.55, P < 0.001), maximum stroke volume (slope =-0.93, intercept = 183.3, r = 0.50, P = 0.002), or the subjective clinical assessment (slope =-1.06, intercept = 182.0, r = 0.72, P < 0.001). Consistent trends were observed between all three parameters for 12 out of the 15 patients. CONCLUSIONS: These results suggest that in patients indicated for CRT, rate-adaptive functions may be useful to shorten AV intervals with increased rate, in order to maximize left ventricular filling, stroke volume, and clinical left ventricular function. Further studies are necessary to determine the clinical impact of these rate-adaptive algorithms.

Sustained reverse left ventricular structural remodeling with cardiac resynchronization at one year is a function of etiology: quantitative Doppler echocardiographic evidence from the Multicenter InSync Randomized Clinical Evaluation (MIRACLE).

BACKGROUND: Cardiac resynchronization therapy (CRT) is an effective therapy for patients with moderate to severe heart failure and prolonged QRS duration. The purpose of this study was to determine whether reverse left ventricular (LV) remodeling and symptomatic benefit from CRT were sustained at 12 months, and if so, in what proportion of patients this occurred. METHODS AND RESULTS: Serial Doppler echocardiograms were obtained at baseline and 6 and 12 months after CRT in 228 patients enrolled in the Multicenter InSync Randomized Clinical Evaluation (MIRACLE) trial. Measurements were made of LV end-diastolic (EDV) and end-systolic (ESV) volumes, ejection fraction, LV mass, severity of mitral regurgitation (MR), peak transmitral velocities during early (E wave) and late (A wave) diastolic filling, and myocardial performance index. At both 6 and 12 months, respectively, CRT was associated with reduced LV EDV (P<0.0001 and P=0.007) and LV ESV (P<0.0001 and P<0.0001), improved ejection fraction (P<0.0001 and P<0.0001), regression of LV mass (P=0.012 and P<0.0001), and reduced MR (P<0.0001 and P<0.0001). LV filling time, transmitral E/A ratio, and myocardial performance index all improved at 12 months compared with baseline (P<0.001, P=0.031, and P<0.0001). Reverse LV remodeling with CRT occurred in more patients at 6 than at 12 months (74% versus 60%, respectively; P<0.05) and was greater in patients with a nonischemic than an ischemic etiology. CONCLUSIONS: Reverse LV remodeling and symptom benefit with CRT are sustained at 12 months in patients with New York Heart Association class III/IV heart failure but occur to a lesser degree in patients with an ischemic versus a nonischemic etiology, most likely owing to the inexorable progression of ischemic disease.

Effect of cardiac resynchronization therapy on left ventricular size and function in chronic heart failure.

BACKGROUND: Cardiac resynchronization therapy (CRT) has recently emerged as an effective treatment for patients with moderate to severe systolic heart failure and ventricular dyssynchrony. The purpose of the present study was to determine whether improvements in left ventricular (LV) size and function were associated with CRT. METHODS AND RESULTS: Doppler echocardiograms were obtained at baseline and at 3 and 6 months after therapy in 323 patients enrolled in the Multicenter InSync Randomized Clinical Evaluation (MIRACLE) trial. Of these, 172 patients were randomized to CRT on and 151 patients to CRT off. Measurements were made of LV end-diastolic and end-systolic volumes, ejection fraction, LV mass, severity of mitral regurgitation (MR), peak transmitral velocities during early (E-wave) and late (A-wave) diastolic filling, and the myocardial performance index. At 6 months, CRT was associated with reduced end-diastolic and end-systolic volumes (both P<0.001), reduced LV mass (P<0.01), increased ejection fraction (P<0.001), reduced MR (P<0.001), and improved myocardial performance index (P<0.001) compared with control. beta-Blocker treatment status did not influence the effect of CRT. Improvements with CRT were greater in patients with a nonischemic versus ischemic cause of heart failure. CONCLUSIONS: CRT in patients with moderate-to-severe heart failure who were treated with optimal medical therapy is associated with reverse LV remodeling, improved systolic and diastolic function, and decreased MR. LV remodeling likely contributes to the symptomatic benefits of CRT and may herald improved longer-term survival.

Functional and echocardiographic improvement following multisite biventricular pacing for congestive heart failure.

BACKGROUND: Heart failure remains a major cause of morbidity and mortality despite advances in pharmacological treatment. Recently, multisite biventricular pacing has been used in the treatment of patients with heart failure. OBJECTIVES AND METHODS: The short and medium term effects of this treatment modality were assessed, and the association between baseline clinical characteristics and the positive response to treatment was investigated. Consecutive patients who received this treatment modality were included. They underwent comprehensive clinical and echocardiographic assessment including a 6 min walk at baseline, one month and three months. RESULTS: Between January 1998 and June 1999, 95 patients received multisite biventricular pacing therapy in the three participating hospitals. In 63 patients with complete three-month follow-ups, there were improvements from baseline to three-month follow-up in New York Heart Association heart failure (3.3 +/- 0.5 to 2.2 +/- 0.6, P<0.001) and 6 min walk (305 +/- 120 to 403 +/- 113 m, P<0.001). Significant salutary changes in echocardiographic measurements were also observed in left ventricular (LV) diastolic dimension, ejection fractions (EFs), interventricular contraction delay and severity of mitral regurgitation (MR). The 63 patients were categorized into responders (n=42) and nonresponders (n=21) based on the clinical response. Clinical characteristics were similar between the two groups. The responders had a more pronounced decrease in QRS width. An increase in LVEF and a reduction in LV diastolic dimension, interventricular mechanical delay and severity of MR were observed in the responders but not in the nonresponders. Furthermore, there was a positive association between the reduction in QRS width and the increase in LVEF. CONCLUSIONS: Cardiac resynchronization by means of multisite pacing appears to be a promising therapy in the treatment of heart failure. The salutary clinical response is associated with echocardiographic improvement.