Influence of Cardiac Pacing Mode on Left Atrial Appendage Flow Velocity: Implication to Systemic Embolism During VVI Pacing

Previous studies have shown that the incidence of thromboembolism is higher in patients with single-chamber ventricular demand (VVI) pacemakers than in patients with dual-chamber (DDD) pacemakers. However, data on left atrial appendage flow velocity in pacing patients are limited. To investigate the influence of the pacing mode on the left atrial appendage flow velocity, we studied 19 patients with permanent DDD pacemakers and measured the left atrial appendage flow velocity by transesophageal echocardiography at baseline (during DDD pacing) and after switching to VVI pacing. The indications for pacemaker implantation were second- and third-degree atrioventricular block (AVB group, n = 11) and sick sinus syndrome (SSS group, n = 8). Compared with the DDD pacing mode, there was a significant decrease in the left atrial appendage flow velocity during VVI pacing in both the SSS group (43 ± 14 vs 23 ± 7 cm / sec, P < 0.05) and the AVB group (59 ± 18 vs 41 ± 18 cm / sec, P < 0.05). In eight patients with persistent retrograde ventriculoatrial conduction during VVI pacing, the left atrial appendage flow velocity was markedly decreased (from 43 ± 16 to 25 ± 9 cm / sec, P < 0.05). In five (63%) of the eight patients, left atrial appendage flow velocity was less than 25 cm/sec. A reduction in left atrial appendage flow velocity when switching from DDD to VVI pacing may account for an increased risk of thrombus formation in the left atrial appendage (an increased thromboembolic risk in patients in sinus rhythm with VVI pacemakers).     

"Subclinical" pacemaker syndrome: a randomised study of symptom free patients with ventricular demand (VVI) pacemakers upgraded to dual chamber devices.

OBJECTIVE--To determine whether symptom free patients with single chamber pacemakers benefit from dual chamber pacing. DESIGN--A randomised double blind crossover comparison of ventricular demand (VVI), dual chamber demand (DDI), and dual chamber universal (DDD) modes after upgrading from a VVI device. SETTING--Cardiology outpatient department. PATIENTS--Sixteen patients aged 41-84 years who were symptom free during VVI mode pacing for three or more years. INTERVENTION--Pacemaker upgrade during routine generator change. MAIN OUTCOME MEASURES--Change in subjective (general health perception, symptoms) and objective (clinical assessment, treadmill exercise, and radiological and echocardiographic indices) results between pacing modes before and after upgrading. RESULTS--75% preferred DDD, 68% found VVI least acceptable with 12% expressing no preference. Perceived general well-being and exercise capacity (p less than 0.01) and treadmill times (p less than 0.05) were improved in DDD mode but VVI and DDI modes were similar. Clinical, echocardiographic, radiological, and electrophysiological indices confirmed the absence of overt pacemaker syndrome, although mitral and tricuspid regurgitation was greatest in VVI mode (p less than 0.01). CONCLUSIONS--Most patients who were satisfied with long term pacing in VVI mode benefited from upgrading to DDD mode pacing suggesting the existence of "subclinical" pacemaker syndrome in up to 75% of such patients. The DDI mode offered little subjective or objective benefit over VVI mode in this population and should be reserved for patients with paroxysmal atrial arrhythmias. VVI mode pacing should be used only for patients with very intermittent symptomatic bradycardia or atrial fibrillation with a good chronotropic response during exercise.     

"Subclinical" pacemaker syndrome: a randomised study of symptom free patients with ventricular demand (VVI) pacemakers upgraded to dual chamber devices.

OBJECTIVE--To determine whether symptom free patients with single chamber pacemakers benefit from dual chamber pacing. DESIGN--A randomised double blind crossover comparison of ventricular demand (VVI), dual chamber demand (DDI), and dual chamber universal (DDD) modes after upgrading from a VVI device. SETTING--Cardiology outpatient department. PATIENTS--Sixteen patients aged 41-84 years who were symptom free during VVI mode pacing for three or more years. INTERVENTION--Pacemaker upgrade during routine generator change. MAIN OUTCOME MEASURES--Change in subjective (general health perception, symptoms) and objective (clinical assessment, treadmill exercise, and radiological and echocardiographic indices) results between pacing modes before and after upgrading. RESULTS--75% preferred DDD, 68% found VVI least acceptable with 12% expressing no preference. Perceived general well-being and exercise capacity (p less than 0.01) and treadmill times (p less than 0.05) were improved in DDD mode but VVI and DDI modes were similar. Clinical, echocardiographic, radiological, and electrophysiological indices confirmed the absence of overt pacemaker syndrome, although mitral and tricuspid regurgitation was greatest in VVI mode (p less than 0.01). CONCLUSIONS--Most patients who were satisfied with long term pacing in VVI mode benefited from upgrading to DDD mode pacing suggesting the existence of "subclinical" pacemaker syndrome in up to 75% of such patients. The DDI mode offered little subjective or objective benefit over VVI mode in this population and should be reserved for patients with paroxysmal atrial arrhythmias. VVI mode pacing should be used only for patients with very intermittent symptomatic bradycardia or atrial fibrillation with a good chronotropic response during exercise.     

Twenty four hour variation in plasma atrial natriuretic factor during VVI and DDD pacing.

OBJECTIVE: To investigate whether plasma atrial natriuretic factor (ANF) follows a pattern of circadian variation similar to that of other hormones in patients paced under VVI and DDD pacing modes and to determine if the known effect of pacing mode on ANF secretion is maintained throughout the 24 hour period. PATIENTS AND DESIGN: 20 patients were studied. They had complete atrioventricular block and had been paced for 17 (SD 3.5) months with a dual chamber multiprogrammable pacemaker. They were divided into two groups according to the duration of pacing in either VVI or DDD mode before the measurements: group A, n = 11 (8 men, 3 women, aged 65 (7) years), each paced for 24 h under each of VVI and DDD modes in random order; group B, n = 9 (7 men, 2 women, aged 63 (8) years), each paced for 60 d under each pacing mode before the measurements. Blood samples were taken and ANF concentrations measured every 4 h over a 24 h period, starting at 09.00. Measurements were also made of plasma cortisol, which has a known circadian pattern, so that the 24 h curve could be compared with that of ANF. RESULTS: In contrast to cortisol, ANF values indicated a pulsatile pattern of secretion throughout the 24 h period, with no clear circadian variation. In group B, ANF concentrations were significantly higher during VVI than during DDD pacing throughout the 24 h period, whereas in group A this difference was statistically significant only at certain times of day. CONCLUSIONS: ANF does not show the circadian pattern of variation shown by cortisol and other hormones. Dual chamber pacing contributes to an improvement not only in cardiac haemodynamics but also in the neuroendocrine system, especially in the long term.     

Left atrial appendage function in patients with different pacing modes

Many studies suggest that patients who receive a ventricular pacemaker have a higher incidence of systemic thromboembolism compared to patients receiving a physiological pacemaker. However, the exact mechanism regarding the etiology of thromboembolism remains unclear. We evaluated the left atrial appendage (LAA) functions, using multiplane transesophageal echocardiography (TEE), in patients with different pacing modes. In order to evaluate the ejection fraction (EF), peak emptying (V(E)) and filling (V(F)) flow velocities of the LAA by TEE, we studied 31 patients (mean age 63+/-18.5 years) who had been paced for 5.0+/-2.9 years. Patients with atrial fibrillation, left ventricular dysfunction and mitral valve disease were excluded. The pacing indications were complete atrioventricular block (AVB) in 19 patients (9 VVI, 10 VDD or DDD) and sick sinus syndrome (SSS) in 12 patients (5 VVI, 7 DDD). Mean EF, V(E) and V(F) of the LAA were significantly lower in all patients with ventricular pacing (25.5+/-15.6%, 30.4+/-15.6 cm/s and 29. 1+/-19.2 cm/s, respectively) compared to those with physiologic pacing (48.5+/-16.9%, 59.6+/-16.3 cm/s, 57.9+/-18.5 cm/s, respectively) (P<0.01 in all). When patients were further classified with respect to underlying heart disease whether they had SSS or AVB, all measurements of the LAA (EF, V(E) and V(F)) in both subgroup of patients with SSS and AVB were found significantly lower in those with ventricular pacing than in those with physiologic pacing (Tables 3 and 4). This decrease, especially in LAA flow, was much greater in those with SSS (Mean V(E) and V(F) <20 cm/s). In a patient paced with VVI for SSS, a thrombus was detected within the LAA cavity. In conclusion, these results suggest that the pacing modality appeared to influence the LAA functions in paced patients. Patients with asynchronous ventricular pacing modes had a significantly higher incidence of depressed LAA functions than did patients with physiological pacing, especially more marked in patients with sick sinus syndrome. This may be a factor responsible for increased risk of thrombus formation and thromboembolic events in this patient population.     

Acute short-term effect of VVI pacing mode on P wave dispersion in patients with dual chamber pacemakers

The acute or chronic effect of VVI pacing on P wave duration in the same patient with dual chamber pacemaker has not been studied before. Hence, with the purpose of determining whether VVI pacing increases dispersion of atrial refractoriness, we undertook a comparative study with the aid of a simple noninvasive approach, namely P wave dispersion (PWD) determined from surface electrocardiogram in the same patients who were implanted with dual chamber pacemakers. Pmax duration calculated in VVI paced mode was significantly higher than in VDD paced mode (121+/-21 vs. 111+/-17 ms, P=0.021). PWD (33+/-15 vs. 40+/-23 ms, P=0.062) did not demonstrate any significant difference between VDD and VVI paced modes, respectively. In conclusion, the findings of our study suggest that short-term VVI pacing itself does not have any direct effect on PWD in patients with dual chamber pacemakers. Different pacing modes in the long term might be responsible for altering PWD and the occurrence of atrial fibrillation while affecting the autonomic nervous system.     

Hemodynamic benefit of atrioventricular synchrony: prediction from baseline Doppler-echocardiographic variables

The purpose of this study was to determine if baseline Doppler-echocardiographic variables of systolic or diastolic function could predict the hemodynamic benefit of atrioventricular (AV) synchronous pacing. Twenty-four patients with a dual chamber pacemaker were studied. Baseline M-mode and two-dimensional echocardiograms were obtained and Doppler-echocardiographic measurements of mitral inflow and left ventricular outflow were made in VVI mode (single rate demand) and in VDD (atrial synchronous, ventricular inhibited) and DVI (AV sequentially paced) modes at AV intervals ranging from 50 to 300 ms. Forward stroke volume and cardiac output were determined in each mode at each AV interval from the left ventricular outflow tract flow velocities, and the percent increase in cardiac output over VVI mode was determined. M-mode measurements, including left ventricular end-diastolic dimension, shortening fraction and left atrial size and Doppler measurement of diastolic filling, including peak early velocity and percent atrial contribution, did not correlate with the percent increase in cardiac output during physiologic pacing. The stroke volume in VVI mode correlated significantly with the percent increase in cardiac output during physiologic pacing (r = -0.61, p less than 0.005 for VDD mode and r = -0.55, p less than 0.05 for DVI mode). Five of the 15 patients with VVI stroke volume less than 50 ml but none of the 9 patients with stroke volume greater than 50 ml had ventriculoatrial (VA) conduction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Visualization of left atrial appendage and assessment of its function by transthoracic second harmonic imaging and contrast-enhanced pulsed Doppler.

BACKGROUND: Low flow velocity within the left atrial appendage, as assessed by transoesophageal echocardiography, is a predictor of thromboembolism and of a low success rate of cardioversion of atrial fibrillation. However, the semi-invasive nature does limit its serial application as a screening technique. METHODS AND RESULTS: We investigated the value of transthoracic second harmonic echocardiography and pulsed Doppler at baseline and after intravenous contrast injection to visualize the left atrial appendage and assess blood flow velocities within its cavity. We studied 51 consecutive patients undergoing transoesophageal echocardiography. After transoesophageal echocardiography, transthoracic second harmonic imaging was performed and the left atrial appendage was visualized in 46 patients. Interpretable pulsed Doppler tracings of left atrial appendage flow were obtained at baseline in 39 patients and in 45 patients during Levovist administration. The correlations between peak emptying velocity of left atrial appendage as measured by transoesophageal echocardiography and by transthoracic standard and contrast-enhanced Doppler were 0.81 and 0.91, respectively. The agreement between transoesophageal echocardiography and transthoracic contrast-enhanced pulsed Doppler echocardiography in classifying left atrial appendage flow velocity patterns was 93%. Left atrial appendage thrombus was detected by transthoracic second harmonic imaging in only one of the eight patients shown by transoesophageal echocardiography to have a thrombus. However, all but one of the patients with left atrial appendage thrombus and/or spontaneous echocardiographic contrast at transoesophageal echocardiography had <30cm/s left atrial appendage flow velocity by transthoracic Doppler. CONCLUSIONS: This study shows that left atrial appendage can be visualized by transthoracic second harmonic imaging and that the flow velocity within its cavity is reliably measured by pulsed Doppler in a substantial fraction of patients. Contrast enhancement improves the feasibility and the accuracy of transthoracic evaluation of left atrial appendage flow velocity. The practical value of these results in predicting thromboembolic risk and success of cardioversion of atrial fibrillation needs to be proved by prospective studies.     

Assessment of the left atrial appendage mechanical function by three-dimensional echocardiography.

AIMS: We evaluated the feasibility of three-dimensional echocardiography, in the assessment of left atrial appendage (LAA) function. METHODS AND RESULTS: Forty-five patients underwent multiplane transoesophageal echocardiography. In addition to Doppler and two-dimensional echocardiography, data for three-dimensional echocardiography reconstruction were obtained during transoesophageal echocardiography. Left atrial appendage ejection fraction based on three-dimensional echocardiography volume measurements (EFv) and two-dimensional echocardiography area measurements (EFa), coupled with other echocardiographic data, were related to left atrial appendage late peak emptying velocity, a frequently used indicator of left atrial appendage function. Multiple regression analysis has revealed a significant association of peak emptying velocity with EFv (P<0.0001), spontaneous echocardiographic contrast (P=0.001), tricuspid regurgitation (P=0.03) and left ventricular hypertrophy (P=0.05). No significant relation was observed between peak emptying velocity and EFa, presence or absence of atrial fibrillation, left ventricular dysfunction, mitral stenosis and insufficiency, left atrial dilatation, pulmonary venous peak systolic, diastolic and peak reverse flow velocity at atrial contraction as well as left atrial appendage volumes derived from two-dimensional echocardiography and three-dimensional echocardiography. In a simple linear correlation, the degree of association between peak emptying velocity and EFv was higher as between peak emptying velocity and EFa (r=0.7 vs 0.4, both P<0.001). Observer variabilities for calculating EFv were considerably lower than for two-dimensional echocardiography derived EFa. Ejection fractions determined by two-dimensional echocardiography area measurements at 45 degrees, 90 degrees and 135 degrees cutplane angulations were related to EFv only at 135 degrees. CONCLUSIONS: Left atrial appendage ejection fraction calculation by three-dimensional echocardiography is feasible, more accurate than by two-dimensional echocardiography and has lower observer variability. Furthermore, an optimal cutplane angulation of the left atrial appendage view at 135 degrees has been demonstrated.     

Left atrial spontaneous echo contrast in patients with permanent pacemakers.

OBJECTIVE: To determine the relations between left atrial appendage function, spontaneous echo contrast, and thromboembolism in patients with different modes of permanent pacemakers. PATIENTS AND METHODS: 88 patients with pacemaker implantation and 25 healthy controls in sinus rhythm had transoesophageal echocardiographic examination of the left atrial appendage. Left atrial size, appendage area, peak filling and emptying velocities of the atrial appendage, and the presence or absence of spontaneous echo contrast and thromboembolism were determined. The results in 63 patients with ventricular pacing (group 1, subdivided into subgroup 1A: 42 patients with sinus rhythm, and subgroup 1B: 21 patients with atrial fibrillation) were compared with those in 25 patients with synchronous pacing (group 2), and 25 normal control subjects (group 3). RESULTS: Patients with ventricular pacing had two distinct appendage flow patterns: well defined biphasic filling and emptying waves in subgroup 1A, and irregular very low filling and emptying waves in subgroup 1B. The ejection fraction of the left atrial appendage in subgroup 1A was significantly better than that in subgroup 1B (mean (SD) 40.6 (12.0)% v 7.6 (5.0)%, P < 0.0001). The spontaneous echo contrast was observed in 90% of subgroup 1B patients but in only 19% in subgroup 1A (P < 0.05) and was not found in groups 2 and 3 (P < 0.0001). There was a trend for increased prevalence of spontaneous echo contrast in subgroup 1A v group 2 (P = 0.053). Thrombi were detected in two cases, and cardiogenic embolism occurred in one case in subgroup 1B. All patients with spontaneous echo contrast had ventricular pacing. Multivariate analysis showed that atrial fibrillation was associated with occurrence of spontaneous echo contrast in patients with ventricular pacing (P = 0.005). CONCLUSIONS: The left atrial appendage ejection fraction was lower with ventricular pacing than with synchronous pacing. With ventricular pacing there was a trend towards increased prevalence of left atrial spontaneous echo contrast in patients in sinus rhythm, and a significantly increased prevalence in patients with atrial fibrillation.     

Transthoracic Doppler echocardiographic measurement of left atrial appendage blood flow velocity: comparison with transoesophageal measurement.

AIM: We validated transthoracic echocardiographic measurements of left atrial appendage flow velocity by comparing them with transoesophageal echocardiographic measurements. METHODS AND RESULTS: Eighty-four consecutive patients (mean age, 64.6 years) with various cardiac diseases, who underwent both transthoracic echocardiography and transoesophageal echocardiography were studied. Thirty-two patients were in sinus rhythm, and the remaining 52 patients were in atrial fibrillation. On transthoracic echocardiography, the transducer was placed somewhat superior and outside from the position viewing the conventional parasternal short-axis image of the aortic valve, so that the angle between left atrial appendage midline and Doppler beam could be narrowed. The left atrial appendage flow velocity pattern was recorded by pulsed Doppler mode with a sampling volume placed at the left atrial appendage orifice on both transthoracic echocardiography and transoesophageal echocardiography. In both approaches, the peak emptying velocity (LAA-E) and the peak filling velocity (LAA-F) of the left atrial appendage were measured. In sinus rhythm, the LAA-E was detectable in 25 of the 32 patients (78.1%) and the LAA-F in 20 of the 32 patients (62.5%). Both LAA-E and LAA-F were detectable in 46 of the 52 patients (88.5%) in atrial fibrillation. Good correlations of LAA-E and LAA-F were observed between transthoracic echocardiography and transoesophageal echocardiography measurements in sinus rhythm (r=0.94, r=0.95, respectively; both, P<0.0001) and in atrial fibrillation (r=0.89, r=0.95, respectively; both, P<0.0001). CONCLUSIONS: The left atrial appendage flow velocities could be sufficiently recorded and assessed by transthoracic echocardiography in 84 Japanese unselected consecutive patients with sinus rhythm or atrial fibrillation.     

Permanent cardiac pacing and thromboembolic risk in elderly patients

In patients undergoing permanent cardiac pacing, the maintenance of atrial contractility is important to ensure adequate ventricular filling and to guarantee an optimal ventricular ejection capacity. The appropriate pacing mode, assuring a suitable mechanical atrioventricular coupling, prevents the onset of atrial fibrillation and contributes to reduction of the risk of subsequent systemic and pulmonary thromboembolic episodes. We examined 461 patients (266 males and 195 females, aged between 52 and 97 years, average age 76.5 +/- 18) paced for conduction disturbances of various degrees and etiology. Of them, 323 patients received ventricular demand pacemaker (VVI group, average age 77.9 years); 138 underwent dual chamber pacing (DCP group, average age 75.2 years), 117 of the latter received universal demand pacing (DDD) and 21 atrial synchronous ventricular demand pacing (VDD). The patients were subsequently divided into two age-groups: Group A (/= 75 years, 287 patients). According to pacing mode and successive development of stable atrial fibrillation (AF), we analysed the occurrence of systemic and/or pulmonary thromboembolic episodes and the incidence of fatal events. During our study, performed from January 1986 to August 1993, 70 embolic episodes were observed in the VVI group and six in the DCP group. Eighty-four patients with VVI units developed AF during follow-up, compared with only five patients in the DCP group. Our data indicate that VVI patients have a higher incidence of AF, embolic complications and cerebrovascular mortality, in comparison with the DCP group. VVI pacing should be avoided, especially in older patients, when atrial rhythmical activity is present.     

Cost benefit analysis of single and dual chamber pacing for sick sinus syndrome and atrioventricular block: An economic sensitivity analysis of the literature

The benefits of dual (DDD) over single chamber pacing (VVI)have been demonstrated in haemodynamics, exercise capacity,quality of life and reduced complications in atrioventncularblock and sick sinus syndrome. The literature was reviewed to provide complication rates fordual and VV1 pacing. Cost calculations were based on UnitedKingdom 1991 prices. Over a 10-year period, a computer modelcalculated the incidence and prevalence of atrial fibrillation,stroke, permanent disability, heart failure and mortality insix patient categories: sick sinus syndrome paced VVI, sicksinus syndrome upgraded to DDD, sick sinus syndrome paced DDDfrom outset, atrioventricular block paced VYI and those upgradedto DDD and atrio ventricular block paced initially DDD. Calculationswere based on intention to treat. The 10 year survival with DDD vs YVI pacing was 71% vs 57% insick sinus syndrome and 61% vs 51%, respectively, in atrioventricularblock. In both indications the prevalence of heart failure inthe 10 year survivors was 600 lower with DDD pacing. In sicksinus syndrome patients paced VVI, 36% had severe disabilitywhile only 8% experienced this with DDD pacing. For atrioventricularblock the figures were, respectively, 22% vs 3%. The differencein 10 year cumulative cost between VVI and DDD is 13 times thepurchase price of a VVI pulse generator for sick sinus syndromeand 7 times for atrioventricular block. In the third year afterimplantation the cumulative costs of DDD were lower than forVVI for both indications. Dual chamber pacing for both indications, sick sinus syn dromeand atrioventricular block, is both clinically and cost effective.     

Effect of AV synchronization and rate increase on hemodynamics and on atrial natriuretic peptide in patients with total AV block

We studied nine patients (56 +/- 7 years) with complete AV-block and permanent dual-chamber pacemaker (DDD) under different pacing modes: ventricle pacing (VVI) 70 bpm, DDD 106 +/- 4 bpm, rate adaptive pacing (VVI-FA) 108 +/- 3 bpm. Exercise was performed supine on the bicycle ergometer at 50 watts for 5 min at each setting. DDD-paced patients showed significantly higher mixed venous oxygen saturation, being 45 +/- 2% after the fourth minute, (VVI 38 +/- 2%, p less than 0.01 and VVI-FA paced patients 40 +/- 1%, p less than 0.01). Pressures were normal under DDD pacing during exercise (RAP 7 +/- 2 mm Hg; PCP 14 +/- 3 mm Hg) and showed further increase to abnormal levels during VVI (RAP 13 +/- 2 mm Hg, p less than 0.01; PCP 21 +/- 3 mm Hg, p less than 0.02) and VVI-FA pacing (RAP 10 +/- 2 mm Hg, p less than 0.05; PCP 20 +/- 3 mm Hg, p less than 0.01). Stroke volume increased from 71 +/- 5 ml to 105 +/- 7 ml during VVI and from 64 +/- 7 ml to 81 +/- 7 ml during DDD pacing. Stroke volume remained unchanged (69 +/- 5 ml) during VVI-FA pacing. The peak levels of ANP during and after exercise were significantly higher under VVI (951 +/- 248 pg/ml) than under DDD pacing (650 +/- 140 pg/ml, p less than 0.01) and were not different between DDD and VVI-FA pacing (677 +/- 97 pg/ml). These results show that VVI pacing effects a more pronounced increase of ANP level than other pacing modes. Under moderate exercise, rate-responsive pacing compared to VVI pacing showed no differences in mixed venous oxygen saturation and in atrial pressures. Only DDD pacing showed higher oxygen saturation and a normalization of atrial pressures when compared to other types of single chamber pacing.     

A randomized double-blind crossover comparison of four rate-responsive pacing modes

The aim of this study was to compare, both subjectively and objectively, four modern rate-responsive pacing modes in a double-blind crossover design. Twenty-two patients, aged 18 to 81 years, had an activity-sensing dual chamber universal rate-responsive (DDDR) pacemaker implanted for treatment of high grade atrioventricular block and chronotropic incompetence. They were randomly programmed to VVIR (ventricular demand rate-responsive), DDIR (dual chamber demand rate-responsive), DDD (dual chamber universal) or DDDR (dual chamber universal rate-responsive) mode and assessed after 4 weeks of out-of-hospital activity. Five patients, all with VVIR pacing, requested early reprogramming. The DDDR mode was preferred by 59% of patients; the VVIR mode was the least acceptable mode in 73%. Perceived "general well-being," exercise capacity, functional status and symptoms were significantly worse in the VVIR than in dual rate-responsive modes. Exercise treadmill time was longer in DDDR mode (p less than 0.01), but similar in all other modes. During standardized daily activities, heart rate in VVIR and DDIR modes underresponded to mental stress. All rate-augmented modes overresponded to staircase descent, whereas the DDD mode significantly underresponded to staircase ascent. Echocardiography revealed no difference in chamber dimensions, left ventricular fractional shortening or pulmonary artery pressure in any mode. Cardiac output was greater at rest in the dual modes than in the VVIR mode (p = 0.006) but was similar at 120 beats/min. Beat to beat variability of cardiac output was greatest in VVIR mode (p less than 0.0001), with DDIR showing greater variability than DDD or DDDR modes (p less than 0.05). Mitral regurgitation estimated by Doppler color flow imaging was similar in all modes, but tricuspid regurgitation was significantly greater in VVIR than in dual modes (p less than 0.03). Subjects who preferred the DDDR mode and those who found the VVIR mode least acceptable had significantly greater increases in stroke volume when paced in the DDD mode than in the ventricular-inhibited (VVI) mode at rest (22%) when compared with subjects who preferred other modes (2%, p = 0.03). No other objective variable was predictive of subjective benefit from any rate-responsive pacing mode. Thus, dual sensor rate-responsive pacing (DDDR) is superior objectively and subjectively to single sensor (VVIR, DDIR and DDD) pacing and subjective benefit from dual chamber rate-augmented pacing is predictable echocardiographically.     

A comparison of sympathoadrenal activity and cardiac performance at rest and during exercise in patients with ventricular demand or atrial synchronous pacing

Cardiac sympathetic function was assessed by measuring the coronary sinus overflow of noradrenaline and dopamine at rest and during supine exercise in eight patients with high degree atrioventricular block treated with dual chamber pacemakers (DDD). Patients exercised (30-60 W) during both ventricular inhibited (VVI) and atrial synchronous (VAT) pacing. During exercise cardiac output increased less markedly in the VVI mode than in the VAT mode. The cardiac output response was entirely stroke volume dependent in the VVI mode and mainly heart rate dependent in the VAT mode. Coronary sinus noradrenaline concentrations were higher in the VVI mode at rest and during exercise. Noradrenaline overflow from the heart was enhanced during VVI pacing and increased from about 100 pmol/min (17 ng/min) at rest to 1087 pmol/min during exercise (60 W) in the VVI mode and 545 pmol/min in the VAT mode. Dopamine overflow from the heart was less than 5 pmol/at rest but increased 2-5 fold during exercise. Also arterial concentrations of catecholamine increased more during exercise in the VVI mode, but the differences between pacing modes were less pronounced. Circulating adrenaline seems to be of little importance for cardiac function under these conditions; in healthy individuals the arterial concentrations of adrenaline attained in this study have small effects. Cardiac noradrenaline overflow correlated with pulmonary capillary venous pressures and atrial rates in both pacing modes, indicating a relation between cardiac sympathetic activity and cardiac function. Enhanced cardiac release of noradrenaline may increase cardiac contractility and thereby partially compensate for the lack of heart rate responsiveness to exercise during VVI pacing.     

Optimum pacing mode for patients with angina pectoris

A within patient double blind prospective study of symptoms and exercise tolerance was designed to determine the preferred pacing mode in 10 patients with programmable dual chamber pacemakers who also had angina pectoris. Patients were randomly allocated to one month in each of the following modes: ventricular pacing at 70 beats/min (VVI) or atrioventricular synchronous upper rate 150 beats/min (DDD 150) or 100 beats/min (DDD 100). Medications were unchanged throughout the study; none was taking beta blockers. At the end of each month patients underwent an exercise test. During each month patients recorded symptoms and their preferred pacing mode. DDD 100 was the preferred mode (seven patients). There was significantly less chest pain with this mode than with either of the other modes. There were significantly more episodes of dizziness in VVI, and two patients who developed pacemaker syndrome were unable to complete the pacing period. Three patients developed angina during exercise testing in DDD 150. Atrial synchronous ventricular pacing is better than ventricular pacing for the control of symptoms in patients with angina pectoris provided that the upper atrial tracking rate is limited.     

A comparison of sympathoadrenal activity and cardiac performance at rest and during exercise in patients with ventricular demand or atrial synchronous pacing.

Cardiac sympathetic function was assessed by measuring the coronary sinus overflow of noradrenaline and dopamine at rest and during supine exercise in eight patients with high degree atrioventricular block treated with dual chamber pacemakers (DDD). Patients exercised (30-60 W) during both ventricular inhibited (VVI) and atrial synchronous (VAT) pacing. During exercise cardiac output increased less markedly in the VVI mode than in the VAT mode. The cardiac output response was entirely stroke volume dependent in the VVI mode and mainly heart rate dependent in the VAT mode. Coronary sinus noradrenaline concentrations were higher in the VVI mode at rest and during exercise. Noradrenaline overflow from the heart was enhanced during VVI pacing and increased from about 100 pmol/min (17 ng/min) at rest to 1087 pmol/min during exercise (60 W) in the VVI mode and 545 pmol/min in the VAT mode. Dopamine overflow from the heart was less than 5 pmol/at rest but increased 2-5 fold during exercise. Also arterial concentrations of catecholamine increased more during exercise in the VVI mode, but the differences between pacing modes were less pronounced. Circulating adrenaline seems to be of little importance for cardiac function under these conditions; in healthy individuals the arterial concentrations of adrenaline attained in this study have small effects. Cardiac noradrenaline overflow correlated with pulmonary capillary venous pressures and atrial rates in both pacing modes, indicating a relation between cardiac sympathetic activity and cardiac function. Enhanced cardiac release of noradrenaline may increase cardiac contractility and thereby partially compensate for the lack of heart rate responsiveness to exercise during VVI pacing.     

Optimum pacing mode for patients with angina pectoris.

A within patient double blind prospective study of symptoms and exercise tolerance was designed to determine the preferred pacing mode in 10 patients with programmable dual chamber pacemakers who also had angina pectoris. Patients were randomly allocated to one month in each of the following modes: ventricular pacing at 70 beats/min (VVI) or atrioventricular synchronous upper rate 150 beats/min (DDD 150) or 100 beats/min (DDD 100). Medications were unchanged throughout the study; none was taking beta blockers. At the end of each month patients underwent an exercise test. During each month patients recorded symptoms and their preferred pacing mode. DDD 100 was the preferred mode (seven patients). There was significantly less chest pain with this mode than with either of the other modes. There were significantly more episodes of dizziness in VVI, and two patients who developed pacemaker syndrome were unable to complete the pacing period. Three patients developed angina during exercise testing in DDD 150. Atrial synchronous ventricular pacing is better than ventricular pacing for the control of symptoms in patients with angina pectoris provided that the upper atrial tracking rate is limited.