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

Over a five-year period, hemodynamic exercise capacity studies and a randomized controlled trial have been performed in a total of 50 patients. DVI vs. VVI pacing showed an increase in stroke work index (P less than 0.005) and a fall in left ventricular filling pressure (P less than 0.05) in 17 patients. VDD/DDD pacing vs. VVI showed an exercise capacity benefit in 44 patients (P less than 0.01) including 8 patients with sinus node disease and a lower peak heart rate (P less than 0.02). Maintenance of benefit was also shown of VDD/DDD pacing in the longer term (13 months) vs. acute (P - NS). The controlled trial VDD/DDD vs. VVI showed benefit in shortness of breath (P less than 0.01) and general well being (P less than 0.01). It is concluded that atrial synchronous ventricular pacing (VDD/DDD) is the mode of choice in suitable patients.
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PMID:Physiological benefits of atrial synchrony in paced patients. 618 74

Eleven resting patients with an implanted DDD pacemaker were studied. After 30 minutes of AV sequential pacing at a rate of 80 beats/min with three consecutive atrioventricular delays (AVDs; 100, 150, and 200 msec) peripheral venous blood was drawn for further analyses by specific radioimmunoassays of atrial natriuretic peptide (ANP) and the ANP second messenger, cyclic guanosine monophosphate (cGMP). Relative changes in left ventricular (LV) stroke volume following alterations of AVD were assessed by means of pulsed-Doppler echocardiography through measurement of LV outflow time-velocity integrals (TVI). The optimal AVD (oAVD) was defined in individual patients as that which was associated with the greatest TVI and with improvement over both other AVDs of more than 4%. The oAVD was found in nine patients. For these nine patients no significant differences in either plasma ANP or cGMP between various AVDs were observed. However, we found such differences with respect to values measured at oAVD; both ANP and cGMP levels were lowest at oAVD. Pooling together the data obtained in 11 patients at three AVDs, a positive correlation between ANP and cGMP levels was found (r = 0.7, P < 0.0001, n = 33). Moreover, changes of plasma ANP and cGMP induced by every AVD increment of 50 msec were also correlated (r = 0.6, P < 0.01, n = 22). It is concluded that in AV sequential pacing at rest plasma ANP reaches minimal levels at the AVD, which provides the best LV performance. Although levels of cGMP changed in parallel with those of ANP, low relative values of cGMP differences may limit the usefulness of cGMP assays in optimization of the AVD.
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PMID:Plasma ANP and cyclic GMP levels versus left ventricular performance at different AV delays in AV sequential pacing. 751 46

In sum, systolic dysfunction of the ventricle associated with left ventricular outlet obstruction and often with mitral valve regurgitation may be improved by myotomy, myomectomy, mitral valve replacement, and perhaps by the creation of left bundle branch block via DDD right ventricular pacing. Diastolic dysfunction of the ventricle may be improved by prolonging the diastolic filling period, shortening the isovolumic relaxation period with calcium channel blocking drugs, or perhaps by altering the atrioventricular activation time with a DDD pacemaker. The symptoms and complications of associated arrhythmias may be improved by medication, particularly with beta-blockers, which tend to stabilize the atrial rhythm and perhaps the ventricular rhythms. In treating patients with demonstrated ventricular arrhythmias, other antiarrhythmic agents may be helpful. (Table II summarizes the abnormalities, causes, and treatments of hypertrophic obstructive cardiomyopathy.) Epicardial coronary atherosclerosis is not rare in these patients, and arteriographic confirmation may lead to improvement by surgical bypass treatment. Since stroke volume is nearly fixed, cardiac output depends very much on heart rate. For this reason, each patient needs to receive the appropriate dosage of medications to achieve the optimal heart rate for his or her own physiologic state.
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PMID:Potential mechanisms of improvement after various treatments for hypertrophic obstructive cardiomyopathy. 764 95

To determine whether the magnitude of Beat-to-Beat variability in stroke volume (SV) during VVI pacing can predict hemodynamic benefit from DDD pacing, we undertook Doppler recordings of systolic and diastolic LV flow during VVI and DDD pacing in 20 patients (age 54 +/- 9 years) with DDD pacemakers implanted due to AV block. SV increased by 19% +/- 10% from VVI to DDD (P < 0.01). This increase was greater (29% +/- 9%) in patients with a ratio of early (E)/late (A) filling < 1 compared to those with E/A > 1 (10% +/- 9%) (P < 0.001). Beat-to-Beat variability in SV was greater in VVI (13% +/- 8%) compared to DDD (4% +/- 1%) (P < 0.001). Patients with E/A < 1 showed greater Beat-to-Beat variability in SV during VVI pacing (19 +/- 6%) compared to those with E/A > 1 (8% +/- 4%) (P < 0.001). Beat-to-Beat variability in SV during VVI pacing correlated with both percent change in SV from VVI to DDD (r = 0.89, P < 0.001) and E/A (r = -0.71, P < 0.001). In conclusion, patients with E/A < 1 derive greater hemodynamic benefit at rest from DDD pacing compared with E/A > 1. In addition, patients with complete AV block who show large variations in SV during VVI pacing may obtain greater hemodynamic benefit at rest from DDD pacing than patients with small variations.
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PMID:Beat-to-beat variability in stroke volume during VVI pacing as predictor of hemodynamic benefit from DDD pacing. 769 Sep 40

The stroke volume (SV) was measured by the change in the impedance in thirteen patients with dual chamber pacemakers at different atrioventricular delay (AVD) intervals: 31 to 219 ms or 75 to 220 ms. The mitral inflow was also recorded by Doppler echocardiography at each AVD with measurement of the duration of mitral flow (MFD) and the velocity time integral (VTI). All thirteen patients were studied in the DDD mode; in addition, 5 patients were studied in the atrial sensing ventricular stimulation VDD mode. The SV measurement by impedance plethysmography was reproducible with an average variability of 3.5%: the optimal AVD was determined by this method in 11 patients with DDD and 4 patients with VDD pacing: in 3 patients (2 in DDD and 1 in VDD mode) 2 optimal AVD were obtained. The optimal AVD was 123 +/- 31 ms (63 to 156 ms) in DDD mode and 91 +/- 17 ms (63 to 110 ms) in VDD mode. The analysis of left ventricular filling showed that changes in AVD led to similar changes in mitral VTI. The MFD increased as the AVD was shortened to a constant value at the optimal AVD. In all patients, the optimal AVD was obtained when the MFD became maximal and constant. Measurement of MFD is a simple and rapid means of assessing optimal AVD at rest in patients with dual chamber pacing systems.
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PMID:[Determination of the optimal atrioventricular timing by impedance plethysmography in patients with cardiac pacing; correlations with left ventricular filling]. 770 16

To verify that atrioventricular (AV) synchronous pacing (DDD) with short AV delay improves the condition of patients with severe congestive heart failure, we implanted DDD pacemakers in 10 patients with severe heart failure (New York Heart Association [NYHA] class III to IV). One day after pacemaker implantation, the AV delay was optimized by Doppler echocardiographic measurements over the aortic outflow tract. Patients were evaluated regarding NYHA class, stroke volume, cardiac output, ejection fraction, and quality of life at 1, 3, and 6 months after pacemaker implantation. Although the optimized AV delay was associated with short-term improvement in stroke volume and cardiac output (baseline stroke volume = 22 +/- 7 ml, day 1 = 28 +/- 12 ml; p = 0.03: baseline cardiac output = 1.9 +/- 0.6 L/min, day 1 = 2.2 +/- 1.1 L/min; p = 0.10), the mean stroke volume, cardiac output, NYHA class, and ejection fraction did not change significantly after 1, 3, and 6 months of pacing compared with baseline values. Three patients improved in NYHA class during the follow-up. A consistent improvement in stroke volume, cardiac output, NYHA class, and ejection fraction was observed in only 1 patient. In conclusion, we found no beneficial effects of AV-synchronous pacing with optimized AV delay in patients with severe heart failure.
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PMID:Results of atrioventricular synchronous pacing with optimized delay in patients with severe congestive heart failure. 773 1

Pacing the right ventricle in the apex profoundly modifies the sequence of activation and thus the sequence of contraction and relaxation of the left ventricle. To evaluate the relative importance of preserving normal ventricular activation sequence and optimal atrioventricular (AV) synchrony in permanent pacing, we compared the effects of three pacing modes: AAI, preserving both normal AV synchrony and normal activation sequence; DDD, with complete ventricular capture that preserves only AV synchrony; and VVI, disrupting both, at rest and during exercise. Hemodynamic and radionuclide studies were performed in 11 patients who had normal intrinsic conduction and who were implanted on a long-term basis with a DDDR pacemaker for isolated sinus node dysfunction. AAI versus DDD and VVI significantly increased cardiac output at rest (6.6 +/- 1.3 L/min vs 6 +/- 0.9 L/min vs 5 +/- 1 L/min; p < 0.01) and during exercise (13.5 +/- 2 L/min vs 12.1 +/- 2.2 L/min vs 14.4 +/- 2.1 L/min; p < 0.01). Pulmonary capillary wedge pressure was lowest with AAI (15.4 +/- 4.5 mm Hg), with an average reduction of 17% compared with DDD (19.6 +/- 5 mm Hg; p < 0.01) and of 30% compared with VVI (25.8 +/- 7 mm Hg; p < 0.01) during exercise. Identical benefits were observed for all other hemodynamic parameters: right atrial pressure, pulmonary artery pressure, left ventricular (LV) stroke work index, and systemic vascular resistances. LV ejection fraction was significantly higher in AAI than in DDD at rest (61% vs 58%, respectively; p < 0.05) and during exercise (65% vs 60%, respectively; p < 0.05). This improvement in LV systolic function resulted principally from the increase in septal ejection fraction. LV filling also was improved in AAI as demonstrated by a significant increase in peak filling rate at rest and during exercise. These data show the importance of preserving, whenever possible, not only normal AV synchrony but also normal ventricular activation sequence in permanent cardiac pacing.
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PMID:Hemodynamic importance of preserving the normal sequence of ventricular activation in permanent cardiac pacing. 775 44

Three patients with inadvertently positioned left heart pacemaker leads were admitted for neurological symptoms consistent with embolic stroke. In one of them, the pacemaker lead crossed the interatrial septum, the mitral valve, and entered the left ventricle. In another it was erroneously placed through the subclavian artery, across the aortic valve, and into the left ventricular chamber. In the third patient, the right ventricular lead of a DDD pacemaker was placed in the coronary sinus and the right atrial lead crossed the interatrial septum, and intermittently entered the left ventricular cavity. Once anticoagulation was initiated, symptoms resolved; they recurred when the level of anticoagulation dropped leading to a major stroke in one of the patients. Two of the patients were on aspirin at the onset of symptoms. We believe that every approach must be considered to remove the malpositioned lead. Otherwise, full dose anticoagulation must be initiated since antiplatelet therapy alone does not confer adequate protection against stroke.
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PMID:Left heart pacing and cardioembolic stroke. 780 May 75

Ten DDD paced patients, suffering from dilated cardiomyopathy in the NYHA functional classes III or IV were studied by means of Doppler echocardiography at different programmed values of atrioventricular (AV) delay (200, 150, 120, 100, and 80 msec). The following variables were evaluated: LV diameter, ejection fraction, mitral and aortic flow velocity integrals, and stroke volume. During VDD pacing, a resting AV delay associated with the best diastolic filling and systolic function was identified and programmed individually. Shortening of the AV delay to about 100 msec was associated with a gradual and progressive improvement. Further decrease caused an impairment of systolic function. The patients were clinically and hemodynamically reevaluated after 2 months of follow-up. A reduction of NYHA class and an improvement of LV function were consistently found. The reported data suggest that programming of an optimal AV delay may improve myocardial function in DDD paced patients with congestive heart failure. This result may be the consequence of an optimization of left ventricular filling and a better use of the Frank-Starling law.
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PMID:AV delay optimization and management of DDD paced patients with dilated cardiomyopathy. 784 3

In 20 patients we measured the increase in stroke volume at rest with DDD compared with VVI pacing, using pulsed Doppler echocardiography at a pacing rate of 70 beats min. By using the apical two-chamber window, the stroke volume was assessed by measuring the integral wave of flow at the level of the aortic anulus, also the most favourable A-V delay was determined. The increase of stroke was comprised within 25.3% and 48.6%. The patients with increased heart size (atrial or ventricular chamber) or ventricular thickness and clinical or echocardiographic signs of heart failure were excluded to avoid variables too and to have an homogeneous group. This study confirms the hemodynamic effects of ventricular pacing, with and without atrio-ventricular synchrony in patients with normal left ventricular function. Doppler technique is useful in non invasive assessment of cardiac output in patients with or without physiologic pacemakers.
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PMID:[Bicameral (DDD) vs. monocameral (VVI) stimulation: echo Doppler study]. 812 54


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