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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Because dual-chamber (DDD) pacing has been shown to be of benefit regarding symptoms, rest and pacing hemodynamics, and exercise duration in patients with obstructive hypertrophic cardiomyopathy (HC), the effect of DDD pacing was assessed in patients with nonobstructive HC who were significantly symptomatic despite medical management. Echocardiography, treadmill exercise testing, thallium-201 scintigraphy, radionuclide angiography, and invasive measurement of rest and semi-erect bicycle exercise hemodynamics were performed in 12 patients before and approximately 4 months after permanent DDD pacing. One patient died 3 months after pacemaker implantation, because of worsening diastolic heart failure. Of the remaining 11 patients, 10 improved regarding symptoms, and treadmill exercise duration was longer during DDD pacing than during the baseline study in sinus rhythm (6.8 +/- 2.8 to 8.5 +/- 2.8 minutes; p < 0.01), with a significant increase in the peak double product achieved (28.9 +/- 6.1 to 31.0 +/- 6.8 x 10(3); p < 0.05). However, there were significant reductions in cardiac (3.7 +/- 0.9 to 3.1 +/- 0.5 ml/min/m2; p < 0.01) and stroke volume (47.4 +/- 11.4 to 38.7 +/- 6.5 ml/beat/m2; p < 0.01) indexes, and a trend toward reduction in submaximal stroke volume index during DDD pacing as compared with the baseline study in sinus rhythm (44.7 +/- 13.5 to 40.9 +/- 10.9 ml/beat/m2; p = 0.097). No change in peak heart rate, cardiac or stroke volume index, mean blood pressure, or pulmonary artery or pulmonary capillary wedge pressure occurred with peak exercise during DDD pacing as compared with the initial exercise study in sinus rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Results of permanent dual-chamber pacing in symptomatic nonobstructive hypertrophic cardiomyopathy. 814 3

Hemodynamic assessment of pacemaker patients is necessary for gauging responses to changes in programming or other conditions affecting circulation. Impedance cardiography permits noninvasive determinations of cardiac output at short intervals but data regarding variability of this method in patients with pacemakers is unavailable. Thirty-eight patients with pacemakers (24 with DDD and 14 with VVI devices) and 6 normal subjects were studied. Each patient was studied in the supine position and repeated impedance measurements were obtained. Fourteen patients were studied during sinus rhythm, 24 were studied during DDD pacing, and 32 patients were studied during VVI pacing. Variability was assessed by methods that analyzed both serial measurements and variability between 2 consecutive and nonconsecutive measurements. The mean indexes and coefficients of variation of 2 and serial measurements in sinus rhythm and DDD were 4%; in VVI it was 6%. The precision of impedance cardiography in all pacing modes, as demonstrated by analysis of variability, indicates that detected changes of stroke volume and cardiac output > 7% on serial (2 and more) measurements, performed by the same operator and during the same session, represent true hemodynamic alterations with 95% confidence. The precision of impedance cardiography demonstrated may be comparable or superior to other frequently used techniques, and the data obtained are valuable both investigationally and clinically.
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PMID:Variability of cardiac output as determined by impedance cardiography in pacemaker patients. 832 81

In Germany, there have been few investigations into prevalence and medical-therapy for cardiovascular disease (especially regarding cardio infarction) among the elderly. Our aim was to investigate the frequency of cardiovascular disease among over 60 year olds and to show their therapy as population related. The basis of our data was the documents of a representative study group of AOK (insurance) members from a North Rhine Westphalian Metropolis. The prevalence of cardiovascular problems was with 90% very high. 56% showed symptoms of at least two further illnesses from the three categories: the musculo-sceletal system, gastro-intestinal system, and their state of mind. All cardiovascular patients were treated with cardiovascular drugs; 2/3 continuously over a 4-quarter period. 43.9% of the aged population had hypertonia, women (47.1%) being slightly more affected than men (35.4%). The prevalence increased to 50% among 80 year olds. The degree of treatment in the case of female hypertensives was 90% and 82% in the case of males. The prevalence of cardiac infarction came to 3.5% among the elderly, and was notably higher for men than for women (6.7%/2.3%). Almost 90% of the cardiac infarction patients received on average anti-anginal vasodilators with 523 DDD per year. The vast majority of patients received three types of medicines simultaneously. The 1-year mortality of the elderly cardiac infarction patients was, when compared to a random sample of the same age, 7 times higher. Apoplexy among the aged had a prevalence of 2.8% and increased rapidly with age (60-69 years/1% to 5% > or = 70 years). The increase affected, above all, men, whose year's mortality was 15 times higher than that of a random sample of the same age. The apoplexy patients had a large amount of cardiovascular medications prescribed to them.
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PMID:[Prescribed drugs and diagnoses in over 60-year-old persons exemplified by cardiovascular diseases. Follow-up studies using federal health insurance data]. 858 58

Cardiac output (CO) responses to exercise can be altered by ventricular pacing in pacemaker-dependent patients. The relative contributions of CO and peripheral vascular resistance (PVR) toward the initial increase in blood pressure with the initiation of static exercise were investigated in eight otherwise healthy pacemaker-dependent subjects [age 24 +/- 2 yr (range 17-37 yr)]. Beat-by-beat measures of heart rate (HR; electrocardiography), mean arterial pressure (MAP), and CO derived from stroke volume (SV) (CO = HR.SV; 2-D echocardiography) were determined during the first 20 s of a one-legged static knee extension performed at 20% maximal voluntary effort by using three pacing modalities: dual pacing and sensing mode (DDD, i.e., normal physiological HR response), fixed at resting HR (DOO-R), and fixed at peak exercise HR (DOO-E), as previously achieved during 5 min of sustained contraction in the DDD mode. There were no differences in MAP, CO, or PVR (PVR = MAP/CO) between modes at rest (P > 0.05). With DOO-E pacing, SV was lower at rest compared with the other modes and increased with exercise (P < 0.05). Although there were no significant increase in MAP or CO during DOO-R pacing, both variables were elevated by leg contraction during DDD and DOO-E pacing (P < 0.05), with no significant change in PVR. Additionally, the CO and MAP increases were significantly greater with DOO-E pacing (P < 0.05). Thus the magnitude of the initial increase in arterial pressure at the onset of mild one-legged static exercise was dictated by the changes in CO as PVR remained unchanged.
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PMID:Cardiovascular responses at the onset of static exercise in patients with dual-chamber pacemakers. 859 27

The benefits of dual (DDD) over single chamber pacing (VVI) have been demonstrated in haemodynamics, exercise capacity, quality of life and reduced complications in atrioventricular block and sick sinus syndrome. The literature was reviewed to provide complication rates for dual and VVI pacing. Cost calculations were based on United Kingdom 1991 prices. Over a 10-year period, a computer model calculated the incidence and prevalence of atrial fibrillation, stroke, permanent disability, heart failure and mortality in six patient categories: sick sinus syndrome paced VVI, sick sinus syndrome upgraded to DDD, sick sinus syndrome paced DDD from outset, atrioventricular block paced VVI and those upgraded to DDD and atrioventricular block paced initially DDD. Calculations were based on intention to treat. The 10 year survival with DDD vs VVI pacing was 71% vs 57% in sick sinus syndrome and 61% vs 51%, respectively, in atrioventricular block. In both indications the prevalence of heart failure in the 10 year survivors was 60% lower with DDD pacing. In sick sinus syndrome patients paced VVI, 36% had severe disability while only 8% experienced this with DDD pacing. For atrioventricular block the figures were, respectively, 22% vs 3%. The difference in 10 year cumulative cost between VVI and DDD is 13 times the purchase price of a VVI pulse generator for sick sinus syndrome and 7 times for atrioventricular block. In the third year after implantation the cumulative costs of DDD were lower than for VVI for both indications. Dual chamber pacing for both indications, sick sinus syndrome and atrioventricular block, is both clinically and cost effective.
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PMID:Cost benefit analysis of single and dual chamber pacing for sick sinus syndrome and atrioventricular block. An economic sensitivity analysis of the literature. 1054 18

Animal data indicate that chronic, overnight pacing at normal evening heart rates impairs cardiac function. We examined the relationship of pacing rate and cardiac function in nine patients with dual-chamber pacemakers. We investigated two, 3-week pacing regimens (80 and 50 ppm: DDD mode) in a cross-over design. Doppler echocardiograms were performed at 1700 hours (PM) and 0600 hours (AM) at the end of each regimen. Ventricular function and preload decreased overnight (PM vs AM) with both pacing regimens. Compared to the morning values, the ratio of preejection to ejection time (PEP/ET) rose (0.43 vs 0.46), while the mean velocity of circumferential fiber shortening (Vcf) fell (1.16 cm/s vs 1.11 cm/s). Stroke volume (SV) (61 mL vs 53 mL) and ejection fraction (EF) also fell (0.56 vs 0.53) in the morning. End-diastolic volume (EDV) (94 mL vs 88 mL) decreased in the morning, as did the ratio of passive to active filling (E/A) (1.06 vs 0.96). Isovolumic relaxation time (91 ms vs 101 ms) increased overnight at both pacing rates. Systolic function decreased at 80 ppm relative to 50 ppm at both times of day. SV fell (54 mL vs 61 mL), while both EDV (92 mL vs 90 mL) end-systolic volume (ESV) increased (43 mL vs 40 mL). Contractility measured by Vcf (1.09 cm/s vs 1.18 cm/s) and PEP/ET (0.49 vs 0.41) was reduced at 80 ppm. The heart needs to rest at night by slowing its rate of contraction. Pacing at 80 ppm impairs systolic and diastolic ventricular function compared to 50 ppm. Longer term consequences of ostensibly physiological pacing rates merit inquiry, particularly in those with preexisting cardiac dysfunction.
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PMID:Overnight heart rate and cardiac function in patients with dual chamber pacemakers. 873 50

This study was designed to demonstrate the effects of varying the atrioventricular delay (AVD) on ventricular diastolic filling dynamics and the resultant stroke volume in patients with complete heart block and normal cardiac function. We studied 7 patients with normal cardiac function in whom a dual chamber pacemaker had been implanted because of complete heart block. Doppler and M-mode echocardiography was performed at 70, 100, 140, 180, and 220 ms, AVD with the device in DDD mode at a rate of 80 beats/min. The effects of these variable intervals on the contribution of the E and A waveform to the diastolic filling, on the stroke volume, and on the systolic intervals were evaluated. Optimization of this interval, with a 19% increase in stroke volume was achieved in the group of patients at an AVD of 140 ms. When considered individually, the AVD associated with the largest stroke volume, was 100 ms in 2 patients and 140 ms in the remaining 5. At this individual optimal AVD the ventricular septal contraction occurred 31 +/- 14 ms, before the end of the transmitral flow. The optimal AVD is, therefore, the one which synchronizes the ventricular and atrial systole so that the first ventricular septal contraction occurs after the peak of the A wave, just before the end of the transmitral flow. Because of the different functional cardiovascular status of the single patient, this parameter should be individualized; this can be clinically important as it may lead, in this patient population, to an improvement of the stroke volume up to 42%.
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PMID:Systolic and diastolic effects of variable atrioventricular delay in patients with complete heart block and normal ventricular function. 926 21

Ten patients with preserved inotropic function having a dual-chamber (right atrium and right ventricle) pacemaker placed for complete heart block were studied. They performed static one-legged knee extension at 20% of their maximal voluntary contraction for 5 min during three conditions: 1) atrioventricular sensing and pacing mode [normal increase in heart rate (HR; DDD)], 2) HR fixed at the resting value (DOO-Rest; 73 +/- 3 beats/min), and 3) HR fixed at peak exercise rate (DOO-Ex; 107 +/- 4 beats/min). During control exercise (DDD mode), mean arterial pressure (MAP) increased by 25 mmHg with no change in stroke volume (SV) or systemic vascular resistance. During DOO-Rest and DOO-Ex, MAP increased (+25 and +29 mmHg, respectively) because of a SV-dependent increase in cardiac output (+1.3 and +1.8 l/min, respectively). The increase in SV during DOO-Rest utilized a combination of increased contractility and the Frank-Starling mechanism (end-diastolic volume 118-136 ml). However, during DOO-Ex, a greater left ventricular contractility (end-systolic volume 55-38 ml) mediated the increase in SV.
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PMID:Mechanisms for increasing stroke volume during static exercise with fixed heart rate in humans. 929 54

In DDD-pacemaker patients with high degree AV block, Doppler echocardiography of transmitral blood flow can be used to find the individually optimal AV delay (AVO) for left heart AV synchronization. This study tried to validate a Doppler method (ECHO) recently proposed to optimize left ventricular filling by comparing it to stroke volume data derived from impedance cardiography (ICG). It should be further elucidated if optimizing the AV delay (AVD) by means of this method is superior to fixed AVD settings and which differential AVD (pace-sense-offset) should be programmed for atrially triggered (ATP) and AV sequential (AVP) pacing, respectively. AVO as measured in 53 patients showed a linear correlation between ECHO and ICG for both ATP (r = 0.66, P < 0.00001) and AVP (r = 0.53; P < 0.005). The mean deviation in AVO between ECHO and ICG was +/- 26 ms (ATP) and +/- 30 ms (AVP), respectively, with a tendency to longer AVDs with the Doppler method. ECHO limitations could mainly be attributed to: (1) restrictions of AVD programming options (which may be compensated for by slight modification of the proposal); and (2) to pathophysiological mechanisms that alter mitral valve dynamics. Optimization of the AVD by Doppler produced a stroke volume that was significantly higher (19%) than with a fixed AVD (150 ms in ATP; 200 ms in AVP). There was a wide scatter in pace-sense-offsets between-7 and 134 ms, which was reflected by both methods. It is concluded that AVO determinations by ECHO are valid provided that methodological pitfalls and limitations caused by the disease are recognized. Tailoring AVD with respect to diastolic filling improves systolic function and is superior to nominal AVD settings. Fixed differential AVDs as offered by some manufacturers are far from being physiological. Thus modern pulse generators should offer free programmability over a wide range of AV delays.
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PMID:Optimizing the AV delay in DDD pacemaker patients with high degree AV block: mitral valve Doppler versus impedance cardiography. 935 87

This study was performed in a population of sequential dual-chamber pacemaker-patients with isolated mitral regurgitation (MR) to identify the "ideal atrioventricular (AV) delay" and to determine the effect of sequential pacing with the ideal AV delay on MR degree. Twenty consecutive patients (age 69 +/- 7 years; 45% men) hospitalized at our institution for symptomatic III degree AV block and isolated MR were studied. All received a dual-chamber pacemaker programmed in DDD at a rate of 70 pulses/minute. The ideal AV delay was selected using echo-color Doppler parameters; it was defined as that resulting in a lower degree of MR and in the highest cardiac output. The mean "optimal short" AV delay resulted in 98 +/- 7 ms. At short AV delay we observed a significant reduction in MR severity (regurgitant fraction from 48 +/- 12% to 25 +/- 10% and jet area from 15 +/- 2 to 9 +/- 2 cm2; p <0.0001) together with an increase in stroke volume (68 +/- 16 vs 88 +/- 15 ml; p = 0.007) and mitral early-to-late peak velocity ratio (0.79 +/- 0.33 vs 1.38 +/- 0.37; p <0.0001). In conclusion, a short AV delay may be used to improve cardiac output in sequential paced patients with pure, isolated MR.
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PMID:Short atrioventricular delay reduces the degree of mitral regurgitation in patients with a sequential dual-chamber pacemaker. 938 6


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