Vince Paul

Heart rate dependency of pulse pressure amplification and arterial stiffness.

BACKGROUNDnPulse pressure and aortic pulse wave velocity, measures of arterial stiffness, are both important determinants of cardiovascular risk. However, assessment of peripheral pulse pressure does not always provide a reliable measure of changes in central pulse pressure or arterial stiffness. The aim of the present study was to assess the effect of acute changes in heart rate on arterial stiffness and on peripheral and central pulse pressure in healthy subjects.nnnMETHODSnTwenty subjects (age range, 20 to 72 years) were studied at cardiac catheterization. Pulse wave analysis was used to determine central pressure, augmentation index (AIx), a measure of systemic arterial stiffness, and aortic pulse wave velocity (PWV) during right atrial pacing (80 to 120 beats/min).nnnRESULTSnPulse pressure amplification increased during pacing due to a reduction in central pressure augmentation. AIx was significantly and inversely related to heart rate (r = -0.70, P < .001) due to an alteration in the relative timing of the reflected pressure wave, rather than a reduction in arterial stiffness, as PWV did not change.nnnCONCLUSIONSnThese data suggest that peripheral pulse pressure does not provide an accurate assessment of changes in central hemodynamics in relation to changes in heart rate, and that aortic stiffness is not affected by acute changes in heart rate.

Randomized Controlled Study Investigating the Effect of Biatrial Pacing in Prevention of Atrial Fibrillation After Coronary Artery Bypass Grafting

BackgroundAtrial fibrillation (AF) is a common problem after CABG. Prevention with prophylactic drug therapy has had limited success, therefore alternative approaches are required. This study investigated the role of biatrial pacing compared with no pacing on AF incidence after isolated first-time CABG. Methods and ResultsDuring surgery, temporary pacing leads were placed in the lateral wall of the right atrium and at the roof of the left atrium in Bachmann’s bundle to allow bipolar pacing and sensing at each site. After surgery, all patients were connected to an external pacemaker (Chorum ELA) that also acted as a Holter monitor. Patients were consecutively randomized to either 4 days of biatrial pacing at a base rate of 80 bpm or to no pacing (control group, base rate 30 bpm). End points included an episode of AF lasting >1 hour on pacemaker Holter, clinically detected AF, intensive care unit (ICU) and hospital stay, and postoperative complications. One hundred thirty patients were randomized. Biatrial pacing significantly reduced both monitored (13.8% versus 38.5%, P =0.001) and clinical (10.8% versus 33.8%, P =0.002) episodes of AF. Median ICU (19 versus 24 hours, P =NS) and mean hospital stay (7.7±6.9 versus 9.7±10, P =NS) did not significantly change. The number of postoperative complications was lower in the biatrial group (13 versus 35, P =0.001). ConclusionsBiatrial pacing after CABG significantly decreases the incidence of AF. This is associated with reduced postoperative complications and a trend toward reduced ICU and hospital stay.

Evaluation of biatrial pacing, right atrial pacing, and no pacing in patients with drug refractory atrial fibrillation.

It has been suggested biatrial pacing may prevent the recurrence of atrial fibrillation (AF). To further evaluate this hypothesis, we performed a randomized, single-blinded study in 19 patients with drug refractory AF. The study compared biatrial pacing with conventional right atrial (RA) pacing and a control period of inhibited pacing. The pacing modes utilized were DDD with a base rate of 70 beats/min for biatrial and RA pace (with and without biatrial resynchronization, respectively) and 40 beats/min for the control period. The duration of each pacing mode was 3 months. The number of AF episodes and their duration were obtained from pacemaker Holter memory (Chorus RM ELA Medical). Comparison of the control period (n = 11) with either pacing strategy showed a significant decrease in the total duration of AF (control 27 +/- 35 days, biatrial 8 +/- 15 days p = 0.02, RA 11 +/- 27 days p = 0.04). However, there was no effect on the number of AF episodes (control 79 +/- 108, biatrial 36 +/- 75 p = 0.32, RA 41 +/- 80 p = 0.11). The total percentage of atrial pacing also significantly increased when the control period (6 +/- 9%) was compared with both RA pace (62 +/- 33%, p = 0.008) and biatrial pace (63 +/- 31, p = 0.003). When biatrial pacing was compared with RA pace (n = 19), there was no significant difference in either the duration of AF (biatrial 16 +/- 26 days vs RA 19 +/- 31 days, p = 0.7) or the number of AF episodes (biatrial 56 +/- 91 vs RA 87 +/- 106, p = 0.34). In conclusion, pacing (either type) at a base rate of 70 beats/min has an antifibrillatory effect when compared with inhibited pacing at 40 beats/min. No additional benefit of biatrial pacing over right atrial pacing was demonstrated in this study.

Two-Year Performance of a Preshaped Lead for Left Ventricular Stimulation

Important goals, when implanting a cardiac resynchronization therapy (CRT) system, are to reach a stable LV lead position in a suitable coronary sinus (CS) tributary associated with a low capture threshold and no extracardiac stimulation. The aim of this study was to assess the 2‐year performance of a new preshaped lead designed for LV stimulation. The study enrolled 102 patients with heart failure and bundle branch block who underwent implantation of a CRT system, including a sheath‐guided, unipolar, S‐shaped LV lead placed in a CS tributary. At each follow‐up the electrical parameters and CRT system related adverse events were recorded. Eight patients who underwent LV stimulation alone, versus 88 patients who received biventricular CRT systems, were analyzed separately. Access to the CS was reached in 98 patients, and the lead was permanently implanted in 96 (94%) patients. The overall procedural time was 98 ± 28 minutes. During follow‐up, three patients underwent reinterventions for phrenic nerve stimulation (n = 2) and hematoma (n = 1). The capture threshold at implantation was 1.4 ± 0.9 V with LV versus 1.7 ± 0.5 V with biventricular stimulation, and after a transient increase, remained between 1.6 and 1.9 V in both configurations. The device measured impedance was significantly higher with LV than with biventricular stimulation at the time of CRT system implantation (698 ± 296 Ω vs 380 ± 67 Ω, P < 0.05) and during follow‐up. The initial R wave amplitude was 14.3 ± 5.9 mV in LV versus 8.9 ± 3.2 V in the biventricular configuration (NS) and 13.8 ± 7 mV in LV versus 12.8 ± 4.8 mV in the biventricular configuration at 24 months (NS). Implantation of the S‐shaped LV lead for CRT was safe, expeditious, and associated with a high success rate and reliable long‐term performance.

Does atrial overdrive pacing prevent paroxysmal atrial fibrillation in paced patients

The role of atrial overdrive pacing for the suppression of paroxysmal atrial fibrillation remains unclear. To investigate this we have performed a randomised study evaluating the role of an increased atrial base rate in suppressing this arrhythmia in patients implanted with a permanent pacemaker (Chorum ELA) for sick sinus syndrome with previous documented paroxysmal atrial fibrillation. Twenty-seven patients (mean age, 69; 15 female) were randomised to two 3-month single-blinded crossover periods of DDDR pacing. The pacemaker was set with a base rate of 60 bpm (normal) during one period and at 10 bpm (overdrive) above the average heart rate during the other, mean (S.D.) 75+/-7 beats/min (range, 70-96). The fallback algorithm of the pacemaker was activated to record the number and duration of paroxysmal atrial fibrillation episodes. During the overdrive period there was a significant increase in the total duration of atrial pacing (normal 60+/-26% vs. overdrive 72+/-28%, P<0.001). However there was no significant difference in the number of paroxysmal atrial fibrillation episodes (normal 43+/-109 vs. overdrive 43+/-106, P=ns), or their total duration (normal 42+/-108 h vs. overdrive 99+/-254 h, P=ns). In conclusion, atrial overdrive pacing, achieved by increasing the atrial base rate, has no incremental benefit in the suppression of paroxysmal atrial fibrillation when compared to rate responsive pacing with a base rate of 60 bpm.

Effect of Left Ventricular Function on Long-Term Left Ventricular Pacing and Sensing Threshold

AbstractBackground: The effect of left ventricular (LV) systolic function on the long-term left ventricular pacing and sensing threshold is unclear.nMethods and Results: We studied the effect of LV ejection fraction (LVEF) on the LV pacing and sensing threshold in 56 patients (mean age: 70.2 ± 10.5 years) underwent permanent LV pacing using a self-retaining coronary sinus lead (Model 1055 K, St Jude Medical, USA). In 49 patients, the LV lead was implanted for conventional pacemaker indication (sick sinus syndrome = 14, heart block = 26 or slow atrial fibrillation = 9). The remaining 7 patients were implanted for congestive heart failure. The LV pacing and sensing threshold, and lead impedance were compared between patients with LVEF <40% (Group 1, n = 28) and LVEF >40% (Group 2, n = 28) during implant and at 3-month follow up. The LV pacing lead was successfully implanted in all patients without any lead dislodgement on follow-up. At implant, Group 1 patients had a significant lower R wave amplitude, but similar LV pacing threshold and lead impedance as compared to Group 2. However, at 3-month follow-up, Group 1 patients had a significantly higher LV pacing threshold compared to Group 2 patients. There were no significant differences in the sensing threshold and lead impedance between the two groups. Furthermore, there was also a significant interval increase in LV pacing threshold in Group 1 patients (0.94 ± 0.12 V) after 3 months, but not in Group 2 patients (0.16 ± 0.08 V, p < 0.01).nConclusions: The results of this study suggest that the LV systolic function has a significant impact on the long-term LV pacing threshold. The long-term left ventricular pacing threshold in patients with left ventricular systolic dysfunction increased after implant and was higher than patients with normal left ventricular systolic function.

Influence of clinical and angiographic factors on development of collateral channels.

Background The degree of coronary collateralization is believed to be related to several clinical and angiographic factors. The duration and frequency of angina may be important factors in determining development of collateral channels. Objective To assess these factors for a consecutive series of patients suspected to have coronary artery disease. Methods Patients without at least one stenosis of <50% and patients who had previously undergone bypass surgery were excluded from our study. Severity of stenosis was quantified by digital analysis, antegrade flow in terms of TIMI grade, and collaterals using the Rentrop classification. Results We reviewed 106 patients [mean age 61 years (range 35–84), 77.6% men]. Of these, 22 (21%) had presented with an acute coronary syndrome on this admission, whilst 46 patients (43%) had previously had an acute coronary syndrome. Collaterals were more likely in patients with stenoses of >90% (Spearman correlation 0.65, Pu2005 <u20050.001) in patients with lower than normal TIMI flow grade (Spearman correlation 0.86, Pu2005 <u20050.01) and were related to regions of hypokinesis (Spearman correlation 0.35, Pu2005 <u20050.01). Significant collaterals were present in 14 patients (13%) despite their having TIMI grade II/III flow. Two of these patients had grade 2/3 collaterals with TIMI grade II/III antegrade flow. Degree of collateralization was not related to chronicity and frequency of symptoms, age, risk factors for atherosclerosis and nature of presentation (i.e. acute or stable symptoms). Conclusion The likelihood of coronary collateralization cannot be prospectively predicted from clinical history alone, but appears to be largely a function of severity of stenosis and level of antegrade flow. A few patients develop high-grade collateral channels despite the presence of good antegrade flow.

Initial Results with Left Ventricular Pacemaker Lead Implantation Using a Preformed “Peel‐Away” Guiding Sheath and “Side‐Wire” Left Ventricular Pacing Lead

We report our preliminary experience with the use of preformed “peel‐away” guiding sheaths and “side‐wire” pacing leads for permanent biventricular pacemaker insertion in 13 patients with heart failure. Three of these patients were undergoing an upgrade of a preexistent VVIR pacing system after prior His ablation for medically refractory atrial fibrillation. Six of the patients had undergone attempted biventricular pacemaker insertion, but required left ventricular lead repositioning after total implantation failure or late displacement of the lead. The remaining patients were undergoing new system implantation. Target vessel cannulation was achieved in all patients. However, in one patient, diaphragmatic pacing throughout the target vessel length prevented successful implantation. All other implants were ultimately successful (92% success rate). We conclude that device implantation using a preformed sheath and side‐wire pacing lead is feasible and may offer significant benefits over implantation with currently available technology.

Preliminary Results with the Simultaneous Use of Implantable Cardioverter Defibrillators and Permanent Biventricular Pacemakers: Implications for Device Interaction and Development

We report our preliminary experience with the combined use of implantable cardioverter defibrillutors (ICD) and biventricular pacemakers in six patients with heart failure and malignant ventricular arrhythmia. Two patients underwent ICD implantation for malignant ventricular arrhythmia after previous biventricular pacemaker implantation. One patient underwent biventricular pacemaker insertion for NYHA Class III heart failure after previous ICD implantation. Two patients underwent single device implantation. In the sixth patient, a combined implantation failed due to an inability to obtain a satisfactory left ventricular pacemaker lead position. The potential for device interaction was explored during implantation. In two patients a potentially serious interaction was discovered. Subsequent alterations in device configuration and programming prevented these interactions with long‐term use. No complication of combined device use has been demonstrated during a mean follow‐up of 2 months (range 1‐4 months). Satisfactory ICD and pacemaker function has also been demonstrated. We conclude that combined device implantation may be feasible with currently available pacing technology and that further prospective studies are required in this area.

The use of intra-aortic balloon counterpulsation in malignant ventricular arrhythmias

We describe a patient with recurrent ventricular arrhythmias post anterior myocardial infarction who stabilised following intra-aortic balloon counterpulsation. Antiarrhythmic drugs and continuous ventricular pacing were ineffective. The possible mechanisms of the improvement with counterpulsation and other treatment options are discussed.