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R Dianda

Publications and source records attributed to R Dianda.

At least 19 recordsLinked to original sources
PubMed1999

Anomalous "VVI" pacing of a dual chamber pacemaker when programmed in DDI(R) mode.

We describe the case of a dual chamber rate responsive pacemaker (Relay, model 294-03, Intermedics, Angleton, TX, USA) implanted in a 68-year-old male for sick sinus syndrome, which was not working properly when programmed in the DDIR mode, thus determining occasionally a sort of "VVI" pacing. However, the pacemaker performed well when programmed in the DDDR mode. We discovered that this was not a malfunction of a single device but rather a general behavior of this family of Intermedics dual chamber pacemakers (also not rate responsive), caused by a software problem.

Aged↗
PubMed1996

Activated pyrolytic carbon tip pacing leads: an alternative to steroid-eluting pacing leads?

Pyrolytic carbon technology is known for its excellent mechanical properties and electrical conductivity; it is particularly biocompatible and does not require high production costs. The Sorin S100/4 lead is a ventricular passive fixation lead with a hemispherical electrode surface area of 4 mm2; the stimulating tip is made of a graphite core coated by a thin activated pyrolytic carbon layer. We evaluated the acute and medium-term performance of the unipolar version of this lead in 65 patients. At implantation, pacing threshold (at 0.5 ms) was 0.26 +/- 0.08 V; pacing impedance (at 5 V and 0.5 ms) was 537 +/- 94 omega and R wave amplitude was 15.0 +/- 5.5 mV. No lead related complications (dislodgment, perforation, exit block, etc.) occurred in any patient; one patient presented with a wire fracture after 26 months, due to subclavian crush syndrome. Follow-up procedures were performed at 1 week, and 2-, 10-, 18-, and 30-months postimplant. Since the leads were connected to pacemakers from different manufacturers, either voltage or duration thresholds were measured. In approximately two thirds of the patients, with an output of 2.5 V, a mean duration threshold of 0.16 +/- 0.13 ms at 1 week, 0.12 +/- 0.08 ms at 2 months, 0.11 +/- 0.06 ms at 10 months, 0.09 +/- 0.06 ms at 18 months, and 0.07 +/- 0.03 ms at 30 months, was measured. In the remaining one-third of the patients, a comparable voltage threshold trend was measured. The mean pacing impedance showed a transient drop at 1 week, and then increased to a plateau of about 600 omega reached after 10 months. No sensing defect occurred in any patient. Our data show good acute and intermediate-term results of the S100/4 lead; the early rise in threshold was remarkably blunted. Activated pyrolytic carbon tip leads might therefore be considered as a possible, inexpensive alternative to steroid-eluting leads.

Aged↗
PubMed1986

Sinus node pacemaker shift: a phenomenon induced by premature atrial stimulation in man?

The aim of this study was to investigate whether premature atrial stimulation is able to induce a shifting of the sinus node pacemaker. For this purpose we compared, in 18 patients, the curve of sinus node function obtained with Strauss' method with that resulting from the scanning, with premature atrial stimulation, of the first returning cycle following a single premature induced atrial beat. We found that the length of the compensatory phase (zone I) evaluated on the curve resulting from the scanning of the first returning cycle following the single premature induced atrial beat was shorter (15%) than that observed with the original Strauss method. In addition, an inverse relationship between the shortening of the compensatory zone and the estimated sinoatrial conduction time was observed. This result could be accounted for by one of the following explanations: 1) a change in the sinoatrial conduction or in the sinus pacemaker automaticity; 2) sinus node reentry; 3) sinus node pacemaker shift. Even if there is no direct evidence either to prove or to exclude one or more of these explanations, sinus node pacemaker shift seems to be the most convincing explanation.

Adult↗
PubMed1984

[Electrophysiologic characterization of propafenone in man].

We performed an electrophysiologic study in 10 subjects before and after administration of Propafenon in doses of 1,5 mg/Kg b.w. i.v. in 2-3 minutes. No symptoms and no significant reductions of arterial blood pressure were observed. The analysis of our data shows that Propafenon does not significantly influence the sinus node function and the sinoatrial conduction. As far the atrioventricular conduction, the drug caused a significant increase of the Wenckebach point, of St-Q interval duration and of the A-V node absolute refractory period. The H-V interval and the His-Purkinje refractory period were also increased. We conclude that P exerts a negative dromotropic effect by direct pharmacological action on the A-V node and on the intraventricular specific conduction pathways.

Anti-Arrhythmia Agents↗
PubMed1981

[Atrial stimulation and intranodal migration of sinus pacemaker in man (author's transl)].

In order to demonstrate, in man, sinus node pacemaker shift following atrial stimulation, we compared, in 26 patients, the curve of sinus node function obtained with Strauss' method with that resulting by the scanning with premature atrial stimulation of the first returning cycle following either a single premature atrial induced beat (140 ms shorter than the basic cycle) (group A), or a train of 8 consecutive atrial beats induced with a rate slightly faster (10 beats/m) than the control sinus rhythm (group B). Assuming that no changes in sinus pacemaker automaticity or in sinoatrial conduction occur owing to atrial stimulation, curves with the same shape should be observed if the site of the dominant pacemaker remains unchanged: whereas, different lengths of the compensatory phase (zone I) should be expected if an intranodal pacemaker shift occurs. For evaluating the length of the compensatory zone (zone I), we calculate, on the curve of the sinus node function, the mean value of the relation points included in the first third of the reset zone (zone II). According to our results, the length of the compensatory phase (zone I) evaluated on the curve resulting by the scanning of the first returning cycle following either a single premature atrial induced beat (group A), or eight consecutive atrial beats (group B) was shorter than that observed with the original Strauss' method (10% and 18% respectively). However, only in the group B, this difference was statistically significant. In addition, a significant inverse relationship between the shortening of the compensatory zone and the sinoatrial conduction index was also observed. Considering that our results have been corrected in such way as to repeal eventual changes in sinus pacemaker automaticity or sinoatrial conduction following atrial stimulation, the shortening of the compensatory zone, we have observed in our patients, strongly suggests an intranodal sinus pacemaker shift. If we assume that this result could represent an indirect evidence of this phenomenon, some clinical implications may follow: 1) another limitation, in addition to others known (intraatrial conduction delay, sinus arrhythmia, changes in sinus node automaticity, difference between retrograde and antegrade conduction time) could decrease the accuracy of atrial stimulation techniques in the estimation of the sinoatrial conduction time; 2) sinus pacemaker shift following atrial stimulation, may induce an understimulation of the true sinoatrial conduction time; however, according to our results, the error is generally small, so that it does no preclude the usefulness of atrial stimulation techniques in the evaluation of sinoatrial conduction; 3) the more evident and significant shortenings of the compensatory phase occurred with atrial pacing technique: this finding could explain why shorter sinoatrial conduction times are generally observed with Narula's method in comparison with Strauss' method.

Adult↗
PubMed1979

[Diagnostic value of the continuous electrocardiographic monitoring (Holter) and of the electrophysiologic testings in patients with sino-atrial node dysfunction (author's transl)].

A twenty-four hours electrocardiographic recording and an electrophysiological study were performed in 48 patients with sinus bradycardia, 21 of them with symptoms suggesting a sino-atrial dysfunction. Both methods, and independently one each other, were not diagnostic in all symptomatic patients; on the contrary, they showed sinus dysfunction in patients without symptoms related to sino-atrial node dysfunction. These results induce to conclude that the two methods are complementary and that their results must be ever critically accepted, especially when a permanent cardiac pacing is indicated. Because of their not high sensitivity, some patients with sinus dysfunction are not recognised; there-after, the diagnosis is only possible, in these cases, on the base of clinical-signs.

Adult↗
PubMed1977

Analysis of the interpolation phenomenon in man evaluated by premature atrial stimulation.

After early premature atrial stimulations, returning cycles shorter than the basic cycle were observed in 25 patients. In 4 of them sinus echoes were seen to occur after premature atrial stimulation coupling intervals shorter than those able to induce completely interpolated beats. Such a sequence is unexpected if we suggest a sino-atrial entrance block for explaining the interpolation phenomenon. An alternative explanation can be postulated assuming that all these early premature beats are sinus node re-entries and that the completely interpolated beat is only a sinus re-entry fortuitously occurring at an appropriate interval.

Adult↗
PubMed1975

Analysis of sino-atrial conduction in man using premature atrial stimulation.

Sino-atrial conduction was investigated using premature atrial depolarization in 25 patients seven of whom had sino-atrial block. The results obtained in this investigation were evaluated plotting the test cycle (expressed as difference between the basic sinus cycle and the test cycle as a percentage of the basic sinus cycle) as a function of the return cycle (expressed as difference between the return cycle and the basic cycle as a percentage of the basic sinus cycle). In normal subjects, premature atrial depolarizations elicited in the last 10-20% of the spontaneous sinus cycle, produced a progressive prolongation of the return cycle and the points correlating the return cycle index to the test cycle index fell above the diagonal of the plotting system. After earlier premature atrial depolarizations, the return cycle remained of the same length, and the points correlating the return cycle index to the test cycle index fell along a line parallel to the y-axis ('plateau'). The mean value of the returning cycles (as expressed above) corresponding to the test cycles (as evaluated above) included in the first 5% of the 'plateau' can be defined as 'the sino-atrial conduction index'. This index, the sum of conduction into and out of the sinus node, was found to range from 79 to 185 ms. By assuming similar anterograde and retrograde conduction, the sino-atrial conduction time ranged from 39.5 to 97.5 ms (mean value=70 ms). In the patients with sino-atrial block, fully compensatory pauses were observed for atrial premature depolarizations elicited up to the last 25-35% of the atrial cycle, and a slow and progressive divergence from the diagonal of the plotting system was seen instead of the 'plateau'. In these patients the sino-atrial conduction index ranged from 151 to 297 ms (mean 253 ms). By assuming similar antegrade and retrograde conduction, the sino-atrial conduction time ranged from 75.5 to 148.5 ms (mean value=126.5 ms) with a statistically significant difference with respect to normal subjects (P=0.001).

Adult↗
PubMed1975

[Programmed atrial stimulation in the study of sinoatrial conduction in normal subjects (author's transl)].

Sinoatrial conduction was investigated in 18 normal subjects, using premature atrial depolarizations. The results obtained in this investigation were evaluated plotting the test cycle (expressed as difference between the basic sinus cycle and the test cycle as a percentage of the basic sinus cycle) as a function of the return cycle (expressed as difference between the return cycle and the basic cycle as a percentage of the basic sinus cycle). In normal subjects, premature atrial depolarizations elicited in the last 10-20% of the spontaneous sinus cycle, produced a progressive prolongation of the return cycle and the points correlating the return cycle index to the test cycle index fell above the diagonal of the plotting system. After earlier premature atrial stimulations, the return cycle stayed the same length, and the points correlating the return cycle index to the test cycle index fell along a line parallel to "y" axis (plateau). The mean value of the returning cycle (expressed as above) corresponding to the test cycles (evaluated as above) included in the first 5% of the "plateau" can be defined as the "sinoatrial conduction index". This index, the sum of conduction into and out of the sinus node, ranged from 79 msec to 187 msec. By assuming similar anterograde and retrograde conduction, the sinoatrial conduction time ranged from 39.5 msec to 97.5 msec (mean value 70 msec).

Adult↗
PubMed1975

[Functional block in the His-Purkinje system (author's transl)].

In nine patients without clinical or laboratory evidence of heart disease, premature atrial depolarization (PAB) induced a complete block of conduction in the intraventricular conducting system. In these patients the functional refractory period AV (FRPav)) gave short and very similar results to the effective refractory period of the His-Purkinje system (ERPhp), and the effective refractory period AV (ERPAV) was found to be shorter than the ERPhp in all cases. A linear correlation between the ERPhp and the basic cycle length (BCL) was also observed. These special functional properties of the AV node justify the occurrence of intraventricular block after PAB. In fact, the stimulus, rapidly conducted through the AV node, finds a complete or incomplete refractoriness in the ventricular conducting system, and therefore bundle branch or complete intraventricular block occurs. The linear correlation between the ERPHP and the BCL explains why the atrial pacing is not always useful for pointing out intraventricular conducting defects.

Adult↗