Atrial Natriuretic Peptide Levels Reflect Hemodynamic Changes Under Pacemaker Stimulation

Pacemaker stimulation influences plasma levels of atrial natriuretic peptide (ANP). This study evaluated in individuals without impaired myocardial function whether a consecutive increase of pacing rates results in reduced alteration of plasma ANP levels mirroring a putative decrease of atrial contribution to cardiac output. In nine resting patients with DDD pacemakers, absolute and relative ANP plasma levels were determined under DDD (175 msec AV delay) and VVI pacing at a pacing rate of 72, 82, 92, and 113 beats/min. When pacing rates were consecutively increased, higher plasma ANP concentrations were measured. However, the differences in relative ANP levels were nearly identical. Therefore, it seems likely that the atrial contribution to cardiac output at high pacing rates is less important than at lower frequencies, at least when the overall myocardial function is not impaired.     

Electrical Proarrhythmia: Induction of Inappropriate Atrial Therapies due to Far-Field R Wave Oversensing in a New Dual Chamber Defibrillator

R Wave Far-Field Sensing in Dual Chamber Defibrillators . This case report describes delivery of atrial therapies during a sinus tachycardia in a new dual chamber implantable cardioverter defibrillator inappropriately caused by far-field oversensing of ventricular beats in the atrial channel. Upon classification of the PR interval pattern, the rate criterion for an atrial tachycardia was fulfilled, and the device initiated high-frequency burst pacing as the first stage of programmed tiered atrial therapies. Atrial fibrillation subsequently was induced by high-frequency burst pacing, and eventually a programmed 10-J shock was delivered for successful termination of atrial fibrillation. The phenomenon of far-field oversensing of ventricular beats could be repeatedly observed during exercise testing and abolished by decreasing the atrial sensitivity.     

Emergency Placement of Platinum Coils to Prevent Cardiac Tamponade After Wire Perforation of an Occluded Venous Coronary Bypass Graft

A case is reported of a patient with impending cardiac tamponade due to vessel perforation following balloon angioplasty of an occluded venous bypass graft. Prolonged balloon inflation failed to seal the perforation. Leakage was controlled immediately by the delivery of two platinum coils into the perforation. In case of a vessel perforation during an attempt to recanalize an occluded coronary artery bypass, placement of intracoronary platinum coils to seal the perforation may prevent the development of cardiac tamponade.     

Extensive Variation in the Signal Amplitude of the Atrial Floating VDD Pacing Electrode

The dependence of atrial signal amplitude on the site of the ntrial sensing dipole of a single-pass lead was examined in 29 patients. The vertical location of the dipole was documented in supine fluo-roscopy during quiescent and deep breathing and in upright chest roentgenogram, and was expressed as a proportion of the, right atrial height. As the group average, the atrial signal amplitude was equal when tested in supine, sitting, standing, and right- or left-side positions in follow-up determinations. The signal amplitude varied markedly between postures, showing a coefficient of variation of 45%± 24% within the group. Coefficient of variation within the 6-month fallow-up period in each tested position ranged from 31%−4 4%, Correlation between postures was weak (range of r = 0.53–0.81). Vertical location of the atrial dipole had no relationship to the signal amplitude. At least in one posture or test occasion the atrial signal amplitude was very low, ≤ 0.35 mV in 20 patients, and below detection limit (0.25 mV) in 5 patients. Programmed to high sensitivity, atrial undersensing was rare in ambulatory electrocardiography, ranging from 0–9,000 missed atrial beats (0%–8%), with a median of 100 beats/24 hours. In conclusion, temporary variation in atrial signal amplitude is extensive. Despite occasionally measured large signal amplitudes atrial sensitivity in single lead VDD pacemakers should be programmed high, and if poor atrial tracking is suspected, other methods besides routine sensitivity testing should be adapted.     

Time course of left ventricular function and coronary patency after saruplase vs streptokinase in acute myocardial infarction

As part of a prospective randomized double-blind trial (PRIMI)to study the early patency rate of the infarct-related arteryafter saruplase (INN for recombinant unglycosylated full-lengthhuman single-chain urokinase-type plasminogen activator) vsstreptokinase in a subgroup of patients, left ventricular functionwas compared between both treatment groups at 90 min and 24h after thrombolysis and at discharge, and ventricular functionwas related to the coronary perfusion grade. Despite a higher patency rate in the saruplase group 60 minafter initiating thrombolysis, neither global ejection fractionnor hypokinesia at the infarct site were significantly differentbetween the treatment groups at any of the three time pointswhen function was measured. Hypokinesia at the infarct siteremained almost equally severe throughout the study in patientswith perfusion grade O, I, and II, and was consistently significantlymilder in patients with perfusion grade III. In contrast, inpatients with perfusion grade II there was a significant dropin hyperkinesia at the opposite wall at 24 h after thrombolysisand before discharge despite unchanged wall motion at the infarctsite. Although patients treated with saruplase had a higher patencyrate in the infarct related vessel shortly after the start ofthrombolysis, no difference was found in left ventricular functioncompared to patients treated with streptokinase. Complete reperfusion(TIMI grade III) seems to be a prerequisite for left ventricularfunction recovery after thrombolysis, whereas only an occludedvessel (TIMI grade O and I) seems to be related to a longerlasting hyperkinesia at the opposite wall.     

Examination of Explanted Polyurethane Pacemaker Leads Using the Scanning Electron Microscope

Since 1978, 2,365 polyurethane (PU) insulated cardiac pacing leads were implanted transvenously at our institution. To date, there have been no insulation failures in those leads. Thirty-seven PU leads were explanted, mainly for exit block, and 28 of these were investigated using the scanning electron microscope. We found a homogeneous distribution of surface changes in all lead segments in 56% of the 28 examined. These changes were more pronounced at the ligature site; severe surface cracking was noticed in 21%, with the deepest crack being 40 micron (average range of 10-15 micron). There appeared to be no time-dependency of the surface changes as indicated by regression analysis (r = 0.32, p greater than 0.05). The ultimate severity and outcome of this degradation process in the leads reported in this study will only be known in the future after longer use. We conclude that excess stress must be avoided during the implantation procedure and that careful surveillance is necessary.     

Mechanical Wear of Pacemaker Lead Insulation. A Cause of Loss of Pacing

A pacemaker-treated patient is described in whom lead insulation defect caused sudden loss of capture. The defect was caused by mechanical wear of the posterior leaflet of the tricuspid valve and resulted in shunting of the pulse generator with a current drain exceeding the capacity of the pacemaker. In three further cases a similar explanation to sudden loss of pacing was highly suspected.