Influence of Age, Lead Axis, Frequency of Arrhythmic Episodes, and Atrial Dimensions on P Wave Triggered SAECG in Patients with Lone Paroxysmal Atrial Fibrillation

Signal-averaged P wave of 42 patients with lone paroxysmal atrial fibrillation (PAF) and 29 normal subjects (N) were recorded, using three orthogonal leads and analyzed in the time and frequency (entire P wave or a 100-ms segment ranging from 75 ms before to 25 ms after the end of P wave) domains. PAFs were divided into a group of 12 having ≥ 2 attacks a month (HF) and a group of 30 having ≤ 2 attacks a year (LF). Statistically significant differences were absent with regard to ages of PAF and N; ages of HF, LF, and N at the time of signal-averaged ECG; ages of HF and LF at the time of the first arrhythmic episode; and elapsed times from the first episode. Length of P wave and some frequency-domain parameters were found to be significantly correlated with age. PAF showed a significantly longer duration of P wave in the frontal plane using the time-domain analysis. Frequency analysis was found to be useful in evaluating the influence of attack frequency. HF showed significantly higher values of some frequency-domain parameters than LF and N, while the three groups did not differ for time-domain analysis. P wave duration and frequency content of the three orthogonal leads proved to be significantly different in PAF and N. Right and left atrial echocardiographic dimensions proved to be higher (even if within normal limits) in HF than in LF and N. Results suggest that frequency analysis should be performed on the entire P wave.     

Observations on Leukemia in Wistar and Wistar Furth Rats

1. Six-hundred and seventy-three Wistar and W/Fu rats were treated atthe age of 4 months with whole body x-ray, orally administered 3MCA or acombination of these agents. All animals were followed until death and 87per cent were autopsied.

2. Among 303 autopsied animals there were 403 benign and malignanttumors, including 28 leukemias.

3. Differences were noted in the incidence and types of leukemia occurring in both breeds of rats. In Wistars 9 of 11 leukemias were myelogenous and 8 of these followed x-ray exposure.

4. Approximately a 10 per cent incidence of spontaneously occurring mononuclear cell leukemia was found in W/Fu rats; exposure to x-ray apparentlydecreased the occurrence of leukemia in these rodents. Following oral administration of 3MCA, 13 per cent of W/Fu rats developed acute mononuclear cell leukemia.

5. Results of hematologic, cytologic and histochemical studies on ratleukemia are discussed in this article, and the possible significance of theappearance and disappearance of the distinctive mononuclear cells in theperipheral blood is pointed out.

6. Pathologic findings indicate that the majority of deaths, other than thosedue to leukemia, were due to pulmonary infections and a great variety oftumors. In leukemic animals enlargement of the spleen was almost universally present and adenopathy, especially involving mediastinal and retroperitoneal glands, was frequently noted. Among 9 myelogenous leukemiasin Wistar rats green chloromatous tissues were found in 5 animals.

7. Cytogenetic studies were carried out on direct preparations from thebone marrow in most of the leukemic rats in this series. Aneuploidy wasnoted in several animals and one W/Fu rat demonstrated a morphologicallyabnormal "marker" chromosome. In more recent studies improved technicsand use of the spleen as a source of metaphase preparations have affordedbetter opportunities to obtain adequate chromosome preparations in leukemic rats. Further investigations are in progress and special studies arebeing directed to the viral and cytogenetic aspects of leukemia in the rat.

Submitted on December 4, 1964 Accepted on January 25, 1965     

Angiographic Quantification of Thrombus in ST-Elevation Acute Myocardial Infarction Presenting with an Occluded Infarct-Related Artery and Its Relationship with Results of Percutaneous Intervention

Introduction: Routine thrombectomy has been advocated for ST-segment-elevation myocardial infarction (STEMI), but it is unknown how many patients present with a large thrombus. We aimed to quantify the intracoronary thrombus in STEMI and to correlate it with procedure results.
Methods: In 98 patients with STEMI and TIMI flow grades 0–2 in the infarct-related artery, thrombus was qualified as small (ST) when its maximal dimension was <2 vessel diameters and large (LT) when ≥2. Main outcome measures were TIMI flow, myocardial blush grade (MBG), corrected TIMI frame count (cTFC), and ST-segment elevation resolution (STSER).
Results: Only a third of the patients presented with an LT. Thrombus grade was independent of the initial vessel patency. Diabetes (OR 3.1, 95% CI 1.20–8.02, P = 0.027) and pretreatment with clopidogrel (OR 0.27, 95% CI 0.08–0.86, P = 0.034) were independent predictors of LT. LT was an independent predictor of unfavorable results: <3 TIMI flow (OR 2.87, 95% CI 1.04–8.00, P = 0.043), MBG 0–1 (OR 3.36, 95% CI 1.10–10.26, P = 0.033), cTFC > 21 (OR 2.86, 95% CI 1.09–7.49, P = 0.033) and <50% STSER (OR 3.19, 95% CI 1.06–9.63, P = 0.039).
Conclusion: Only a third of STEMI patients present with an LT, being diabetes and lack of clopidogrel pretreatment independent predictors. An LT is strongly associated with worse PCI results.     

Asystole with Syncope Secondary to Hyperventilation in Three Young Athletes

We describe three athletes who had syncope after (case 1) or during (cases 2, 3) hyperventilation. During the episode, ECG showed prolonged sinus arrest. Clinical data and noninvasive investigations were normal and the phenomenon was not reproducible. Electrophysiological study after autonomic blockade allowed a prolonged intrinsic heart rate in case 1, and abnormal corrected sinus node recovery time in cases 1 and 2. During follow-up, symptomatic sinus arrest provoked by deep inspiration occurred in case 3. These cases document prolonged asystole of unknown etiology, secondary to hyperventilation, and probably caused by different vagally-mediated mechanisms.     

Synthesis of human angiotensinogen (1-17) containing one of the putative glycosylation binding sites and its hydrolysis by human renin and porcine pepsin

The N-terminal heptadecapeptide of human angiotensinogen (Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Val-Ile-His-Asn-Glu-Ser-Thr-NH₂), with the C-terminal carboxyl group amidated, was synthesized in order to study the role of Asn-Glu-Ser, a putative carbohydrate binding site, on the hydrolysis by human renin. The synthesis was performed by fragment condensation using the Honzl and Rudinger azide procedure. In our conditions for azide segment condensation, histidine racemization was demonstrated to be negligible for most of the condensation reactions. Human renin liberates angiotensin I from h-angiotensinogen (1-17)-NH₂ with a K_m value of 3.4 × 10^?5m , at pH 7.3 and 37° being similar to h-angiotensinogen (1-13), an analog without the carbohydrate binding site. However, the V_max value of 4.1 × 10^?9mol/G.U. min is one order of magnitude higher. Porcine pepsin was demonstrated to cleave preferentially Leu¹⁰-Val¹¹ bond and, surprisingly, His⁹-Leu¹⁰ as well.