High Resolution ECG and Left Ventricular Volume After Acute Myocardial Infarction

The presence of ventricular late potentials (LPs) early after acute myocardial infarction (AMI) was recently reported to correlate with left ventricular dilatation subsequent to AMI. We assessed prospectively the relationship between LP (time domain) in the late phase of AMI and left ventricular end-diastolic volume (EDV) measured by equilibrium radionuclide angiocardiography 4 weeks and 12 months after AMI. In 80 consecutive patients 4 weeks and 12 months after thrombolytic therapy for AMI, LP and EDV were deter mined (EDV1, EDV2). There was no significant correlation between QRS duration (r = 0.18), RMS40 (r = 0.08), or LAS40 (r = 0.1) and EDV1 or EDV2 in patients with or without LP at baseline. In both groups (patients with [n = 15] and without LP [n = 65]), EDVl and EDV2 were comparable (128 ± 32 mL vs 126 ± 35 mL; 114 ± 40 mL vs 117 ± 36 mL; P = NS). In addition, there was no significant difference between EDVl and EDV2 in patients who developed new LP (n = 6) or lost LP (n = 9) 12 months after AMI. In contrast to LP in the very early phase after AMI, there seems to be no significant correlation between the high resolution ECG in the late phase after thrombolytic therapy for AMI and left ventricular EDV.     

Implantation of a Dual Chamber Pacing and Sensing Single Pass Defibrillation Lead

GRADAUS, R., et al. : Implantation of a Dual Chamber Pacing and Sensing Single Pass Defibrillation Lead. Dual-chamber ICDs are increasingly used to avoid inappropriate shocks due to supraventricular tachycardias. Additionally, many ICD patients will probably benefit from dual chamber pacing. The purpose of this pilot study was to evaluate the intraoperative performance and short-term follow-up of an innovative single pass right ventricular defibrillation lead capable of bipolar sensing and pacing in the right atrium and ventricle. Implantation of this single pass right ventricular defibrillation lead was successful in all 13 patients (  age 63 ± 8 years  ; LVEF  0.44 ± 0.16  ; New York Heart Association [NYHA]  2.4 ± 0.4  , previous open heart surgery in all patients). The operation time was  79 ± 29  minutes, the fluoroscopy time  4.7 ± 3.1  minutes. No perioperative complications occurred. The intraoperative atrial sensing was  1.7 ± 0.5 mV  , the atrial pacing threshold product was  0.20 ± 0.14 V/ms  (  range 0.03–0.50 V/ms  ). The defibrillation threshold was  8.8 ± 2.7 J  . At prehospital discharge and at 1-month and 3-month follow-up, atrial sensing was  1.9 ± 0.9, 2.1 ± 0.5, and 2.7 ± 0.6 mV  , respectively, (  P = NS, P < 0.05, P < 0.05  to implant, respectively), the mean atrial threshold product  0.79, 1.65, and 1.29 V/ms  , respectively. In two patients, an intermittent exit block occurred in different body postures. All spontaneous and induced ventricular arrhythmias were detected and terminated appropriately. Thus, in a highly selected patient group, atrial and ventricular sensing and pacing with a single lead is possible under consideration of an atrial pacing dysfunction in 17% of patients.     

Three-Dimensional Electromagnetic Catheter Technology:

Electroanatomical Mapping. Introduction : The difficult catheter orientation and navigation associated with conventional technology and mono-/multiplane fluoroscopy may complicate ablation procedures of atrial tachycardias. A new three-dimensional catheter technology for electroanatomical mapping of the right atrium and ablation of ectopic atrial tachycardia is described.
Methods and Results : A novel electromagnetic catheter-based mapping system was investigated for electroanatomical mapping of the entire right atrium in 12 patients. The system reconstructed three-dimensional maps from the multitude of endocardial sites that were sequentially mapped and color coded the individual activation times. The electrophysiologic information was superimposed on the geometry of the mapped area. The anatomical landmarks of the right atrium, i.e., the tricuspid annulus. mouth of the coronary sinus, ostia of the superior and inferior venae cavae, and right atrial appendage, could he depicted in all cases. The sinus node area and the preferential conduction along the crista terminalis could be delineated. In four patients with ectopic atrial tachycardia, the earliest endocardial activation could be identified with high spatial resolution as a "hot spot." After completion of the mapping procedure, the ablation catheter could be reliably renavigated to the site of origin, and ablation was successful with one or two impulses. In one patient with previous atrial septal repair, the activation map allowed the reconstruction of a long line of conduction block induced by the atriotoniy.
Conclusion : Three-dimensional electroanatomical mapping of the right atrium allowed detailed reconstruction of the chamber geometry and activation sequence. The sites of origin of ectopic atrial tachycardias could be identified precisely. The system allowed accurate renavigation to the site of earliest activation, thereby guiding successful ablation of the foci.     

Comparative Sensitivity of Eight- and 24-hour Bile Acid Breath Tests and Schilling Test in Ileopathies

The conventional eight-hour bile acid breath test ("acute measurements"), was compared with a modified, extended, 24-hour breath test ("ratio measurements") and the Schilling test to assess relative sensitivity in detecting ileal dysfunction. Sixty-four patients with ileopathies were studied. The presence or absence of bile acid malabsorption was documented by fecal excretion studies of bile acid labels. The sensitivity of the "acute measurements" in the breath test was not significantly different from that of the "ratio measurements" in the ileopathies, regardless of whether or not bile acid malabsorption was present. The "acute measurements" were positive in 49 (77%), the "ratio measurements" in 54 (84%) and the Schilling test in 49 (77%) of the patients. In about 30%, bile acid breath test and Schilling test were not positive in the same patient. A combination of "acute measurements" (breath test) and Schilling test increased the percentage of cases with at least one positive test to 91%. The results of the study show: 1. The sensitivity of the bile acid breath test does not increase if ¹⁴CO₂ measurements are carried out beyond eight hours. 2. Although the breath test and Schilling test are of similar sensitivity in ileopathies, they are frequently not positive in the same patient. Therefore, it would be clinically useful to combine both tests in order to increase the likelihood of diagnosing ileal dysfunction.     

Severe Hypocarbia in Preterm Infants and Neurodevelopmental Deficit

ABSTRACT. We report significant neurological abnormality at 18 months of age in 3 of 7 very low birth weight infants (≤ 1500 g), who during mechanical ventilation inadvertently became severely hypocarbic (arterial carbondioxide tension less than 2.0 kPa (15 mmHg)) at some time during the first 24 h of life. Although the number is small the outcome was significantly worse than the outcome in two fairly similar groups of infants selected as controls ( p =0.026). The infants in one of the control groups were also mechanically ventilated but remained normocapnic. Germinal layer haemorrhage (GLH) was more frequent among these infants compared with the severely hypocarbic infants ( p =0.022). The infants in the other control group was not mechanically ventilated. In all the severely hypocarbic infants the Bayley mental developmental index uncorrected for prematurity was at or below the median for the total sample ( p =0.01). The results suggest that neonatal cerebral ischaemia, for instance due to hypocarbia, is of greater prognostic significance than GLH.     

Solid-phase synthesis of H- and methylphosphonopeptides

We introduce solid-phase syntheses of H- and methylphosphonopeptides, giving access for the first time to a new class of mimics for o-phosphoamino acids. The model peptides H-GlyGlyXaaAla-OH (Xaa = Ser, Thr) were synthesized on a solid-phase using Fmoc/^tBu strategy and HBTU/HOBt activation by incorporation of hydroxyl-protected serine and threonine. As selectively cleavable hydroxyl-protecting groups we used triphenylmethyl and tert-butyldimethylsilyl for both amino acids, as described in the literature. All peptides were phosphitilated with O,O-di-tert-butyl-N,N-diethylphosphoramidite and yielded H-phosphonopeptides after trifluoroacetic acid cleavage. Alternatively we phosphonylated the peptides with O-tert-butyl-N,N-diethyl-P-methylphosphonamidite, which was synthesized by a two-step one-pot procedure starting from commercially available chemicals. All H- and methylphosphonopeptides were obtained in high purities and yields, as shown by reversed-phase high-performance liquid chromatography and anion-exchange chromatography. The phosphonopeptides were characterized by ¹H and ³¹P NMR. We confirmed their molecular masses by electrospray mass spectrometry and analyzed their fragmentation schemes, which seemed to be characteristic for each class of analogues. The H-phosphonopeptides lost phosphonic acid (H₃PO₃, 82 mass units) and the methylphosphonopeptides lost methylphosphonic acid (MeH₂PO₃, 96 mass units). Both H- and methylphosphonopeptides represent a new and simply accessible class of mimics for phosphopeptides. Compared with the corresponding phosphopeptides all phosphonopeptides were synthesized in higher yields and purities (>80%). © Munksgaard 1996.     

Determinants of Dual Chamber Pulse Generators Longevity

The aim of tbis study was to investigate the effect of battery capacity, internal current drain, and stimulation energy on pulse generators longevity, and if battery impedance measurements can reliably predict pulse generators end-of-life. For this purpose, the records of 577 patients with a mean age of 65 ± 14 years who had undergone implantation of two different dual chamber pulse generators (PGl: 409; PG2:168) were retro-spectively reviewed. Battery capacity were 2.3 Ah (PGl) and 3.0 Ah (PG2) while current drain at compara-ble nominal settings was 20 μA (PGl) and 30 μA (PG2) indicating a higher internal current drain of PG2. After a mean follow-up of 46 ± 23 months, stimulation energy at reprogrammed output settings was significantly higher in PGl as compared to PG2 (17.1 ± 0.14 J vs 15.5 ± 0.24 f). Three PGl (0.7%) and 12 PG2 (7.1%) (P < 0.01) had to be exchanged after a mean of 77.3 ± 5.3 months (PGl) and 75 ± 13.5 months (PG2) (P = NS) due to end-of-life being reached. The difference in battery impedances of PGl and PG2 gained statistical significance 5 years after implantation (1.0 kΩ vs 2.4 ± 6.7 kΩ) preceding the significant difference in PG survival after 6 years (98.7 ± 1.3% vs 90.7 ± 4.8%). These results indicate that internal current drain is the most important determinant of the pulse generators longevity and that battery impedance can reliably predict end-of-life. Therefore, the essential information about internal current drain should be available for each pacemaker, since it is required for adequate pulse generator selection. Diagnostic functions of dual chamber pulse generators should include measurement of battery impedance.     

Fractional Flow Reserve: The Ideal Parameter for Evaluation of Coronary, Myocardial, and Collateral Blood Flow by Pressure Measurements at PTCA

To overcome the fundamental limitations of coronary arteriography to assess the functional significance of coronary artery disease, it is necessary to obtain direct information about coronary blood flow. Recently we validated three pressure flow equations, which enable calculation of maximum coronary, myocardial, and collateral flow by merely measuring aortic, central venous, and distal coronary pressures under the condition of maximum vasodilation and using an ultra thin pressure monitoring guide wire for distal coronary pressure recording. In this paper, the first clinical experiences of this method are described. For that purpose, the concept of fractional flow reserve (FFR) is important. Fractional coronary flow reserve (FFR_cor) is defined as the maximum achievable blood flow in a stenotic artery, divided by normal maximum flow in that same artery, i.e. maximum flow in that artery in the case that it would be completely normal. Fractional myocardial flow reserve (FFR_myo) is defined in a similar way, and recruitable collateral blood flow is expressed as a fraction of normal maximum myocardial flow. Fractional flow reserve, defined in this way, is easy to obtain at percutaneous transluminal coronary angioplasty (PTCA) by the pressure-flow equations, is independent of pressure changes, applicable to three vessel disease, and enables calculation of the separate contribution of coronary and collateral flow to total myocardial perfusion. In 18 patients a very close correlation was demonstrated between FFR_myo, calculated by pressure recordings at PTCA by the first pressure flow equation, and FFR_myo obtained by positron emission tomography, which is considered the gold standard for myocardial perfusion. In 60 other patients, maximum recruitable collateral blood flow at balloon inflation (Q_c/Q^N) was calculated according to the third pressure-flow equation and correlated to the presence or absence of ischemia. It could be demonstrated that Q_C/Q^N exceeds 22% in all 23 patients without ischemia, whereas Q_c/Q^N was less than 22% in 34 out of 37 patients who experienced ischemia during balloon inflation. This margin value of 22% is very close to the theoretically expected value of 20%. based upon a coronary flow reserve of 5 under standard physiologic conditions. It can be concluded that the concept of fractional flow reserve provides a rapid, accurate, and elegant way for quantitative assessment of maximum coronary and myocardial blood flow before and after PTCA. Moreover, this is the first method that enables quantitative calculation of collateral blood flow in clinical practice. (J Interven Cardiol 1993; 6:331–344)     

Within- and Between-Patient Variation of the Signal-Averaged P Wave in Coronary Artery Disease

Objectives: To estimate interobserver, within-patient and between-patient variation of the signal-averaged P wave. To determine whether demographic, clinical, conventional ECG information, and coronary angiographic data are associated with the signal-averaged P wave duration in patients with documented coronary artery disease. Background: A prolonged signal-averaged P wave may indicate the presence of a substrate for atrial tachyarrhythmias and may predict subsequent development of atrial fibrillation. However, information on variation, reproducibility, and determinants of the signal-averaged P wave are sparse. Methods: One hundred ninety-three patients with angiographically documented coronary artery disease underwent two consecutive procedures of signal-averaging of P waves (SAECG1 and SAECG2). Interobserver, within-patient, and between-patient variation of the signal-averaged P wave was estimated (coefficient of variation: SD/mean). Multiple linear regression analysis was applied to identify parameters independently associated with signal-averaged P wave duration (SA-P). Atrial late potentials were considered if SA-P > 140 ms, and logistic regression analysis was applied to identify parameters associated with the presence of atrial late potentials. Results: The interobserver, within-patient, and between-patient coefficients of variation for the signal-averaged P wave duration were 7.5%, 6.0%, and 8.4%, respectively. The signal-averaged P wave duration correlated significantly with standard ECG P wave duration and height of the patient (r = 0.59). Forty-nine percent of the patients had atrial late potentials. P wave duration in the standard ECG correctly classified 73% (140/188) of the patients with respect to atrial late potential positivity or negativity. The sensitivity was 67% and the specificity was 78%. Agreement on the presence or absence of atrial late potentials between two observers was present in 71% (136/193) of the patients, and in 78% (151/193) between SAECG1 and SAECG2. Conclusions: The signal-averaged P wave has limited reproducibility in patients with coronary artery disease, and a normal or abnormal signal-averaged P wave can be predicted from the conventional ECG with high accuracy. It is recommended that the signal-averaged P wave be compared with the standard ECG P wave duration in follow-up studies with the aim of predicting atrial fibrillation.