Ventricular Parasystole: A Chronobiologic Study

Previous works have reported circadian rhythms for several cardiovascular parameters. A chronobiologic rhythm is characterized by: mesor (a rhythm-determined average), amplitude (half difference between the highest and lowest values), and acrophase (timing of high point in degrees and/or in hours) along with 95% confidence limits. We performed 24-hour ECG Holler monitoring in seven patients (mean age, 50.6 years) with ventricular parasystole (VP) in order to determine whether the chronotropic activity of parasystolic foci has a circadian rhythm similar to that of the sinus node. For each Holter recording parasystolic rates (PRs) and heart rates (HRs) were calculated every hour. Furthermore, a mean hourly PR and a mean hourly HR were calculated from the hourly PRs and HRs of the patients. The statistic chronobiologic analysis was done by single and mean cosinor methods. Correlation between mean hourly PR and HR was evaluated by Pearson's V coefficient. A statistically significant rhythm (P < 0.05) was found for the single and mean rhythms both of HR and PR. In our patients, HR had acrophase at 1.27 P.M., mesor at 73.28 beats/min, and amplitude at 9.53 beats/min, whereas PR had acrophase at 1.42 P.M., mesor al 38.31 beats/min, and amplitude at 3.64 beats/ min. Chronobiological data and the high direct correlation between mean hourly HRs and mean hourly PRs (r = 0.96, P < 0.001) indicate a similar circadian variability of the chronotropic activity of sinus nodes and parasystolic foci. Although several hypotheses can be made, responsiveness of parasystolic foci to circadian variations of the autonomic nervous system tone (sympathetic and/or vagal) and/or circulating substances (particularly catecholamines) seems the more probable one for explaining our findings.     

Late Sensing Due to Extremely Delayed Right Ventricular Activation in Arrhythmogenic Right Ventricular Cardiomyopathy

A patient with arrhythmogenic right ventricular cardiomyopathy/dysplasia, implanted with a dual-chamber implantable cardioverter-defibrillator programmed in DDD mode, showed an unexpected ventricular sensing dysfunction: despite a very long (320 ms) programmed atrioventricular (AV) interval, ventricular stimuli were delivered in the ST segment after each spontaneous conducted QRS complex. This suggested the presence of ventricular undersensing. When, however, the system was programmed in VVI mode, spontaneous QRS complexes were normally sensed, although electrogram (ECM) analysis revealed that ventricular sensing occurred 160 ms after the beginning of QRS complex. A new ventricular lead was then implanted in the outflow tract of the right ventricle, resulting in normal ventricular sensing function. At the time of intervention, the amplitude of the spontaneous ventricular signal recorded from the old ventricular lead was 2.8 mV. In this patient, no true undersensing occurred although ventricular stimuli were delivered 140 ms after the beginning of spontaneous QRS complexes when the system was in DDD mode: the cause of the apparent pacemaker malfunction was the extremely prolonged ventricular depolarization. Due to fibrofatty muscle replacement, the depolarization wavefront reached the ventricular muscle surrounding the pacemaker lead with such a delay that at the end of the programmed sensed AV interval (320 ms) the ventricular EGM had not yet attained the sensing threshold. This apparent undersensing should, thus, be defined as "late sensing."     

Melanoacanthoma Simulating Pigmented Spitz Nevus: an Unusual Dermoscopy Pitfall

BACKGROUND: The starburst pattern is the dermoscopic hallmark of pigmented Spitz nevus, although it has been rarely observed in melanoma as well. OBJECTIVE: To describe a case of melanoacanthoma simulating pigmented Spitz nevus. MATERIAL AND METHODS: Clinical, dermoscopic, and histopathologic examinations were performed for the occurrence of a 4-mm pigmented skin lesion on the hip of a 38-year-old Caucasian woman. RESULTS: Dermoscopy examination of the lesion disclosed a stereotypical starburst pattern characterized by pigmented streaks symmetrically distributed at the periphery. A preoperative diagnosis of pigmented Spitz nevus was made, and the lesion was excised. However, subsequent histopathologic examination revealed a melanoacanthoma. CONCLUSION: The starburst pattern, although diagnostic for pigmented Spitz nevus, can be rarely observed in other benign or malignant pigmented skin lesions. Accordingly, all lesions in adults exhibiting a starburst pattern or other spitzoid features should be excised for histopathologic evaluation.     

24-Hour Heart Rate Variability in Patients with Vasovagal Syncope

Since alterations in the autonomic nervous system are thought to play a major role in the pathogenesis of vasovagal syncope, we characterized the chronic autonomic profile of 44 patients with syncope and 20 healthy subjects by means of heart rate variability using 24-hour Holter recordings (time- and frequency-domain indexes), and evaluated whether the different types of responses to tilting (vasodepressive versus cardioinhibitory) could be associated with different cardiac autonomic patterns. Twenty-three patients exhibited a positive response to tilting, which was vasodepressive in 11 patients and cardioinhibitory in 12 patients. All vasodepressive patients had a standard deviation of the averages of NN (SDANN) intervals in all 5-minute segments lower than 100 ms. Patients with vasodepressive syncope also had significantly lower values of RMSSD (the 24-hour square root of the mean of the sum of the squares of differences between adjacent normal RR intervals) than those with cardioinhibitory response, and lacked the day-night rhythm of the low frequency/high frequency ratio. However, only SDANN values correctly identified patients with vasodepressive response to tilting. We conclude that (1) the population of patients with vasovagal syncope is heterogeneous, (2) patients with vasodepressive syncope have a peculiar chronic autonomic profile as assessed by 24-hour heart rate variability analysis, and (3) the evaluation of the autonomic profile in 24-hour Holter recordings could be of value in the diagnosis of patients with syncope.     

Postnatal development of intestinal endocrine cell populations in the water buffalo

The frequency and distribution of 11 endocrine cell populations were studied in the intestine of differently aged buffalo, grouped on the basis of diet: 2-d-olds (suckling), 5-mo-olds (weaning) and 5-y-olds (ruminant adult diet). The endocrine cell populations were identified immunocytochemically using antisera against 5-hydroxytryptamine (5-HT), somatostatin, gastrin, cholecystokinin (CCK), COOH-terminal octapeptide of gastrin/CCK, neurotensin, motilin, gastric inhibitory polypeptide (GIP), secretin, glucagon/glicentin (GLU/GLI) and polypeptide YY (PYY). In adult buffalos the regional distribution of endocrine cells is similar to that of other adult ruminants. During postnatal development, these cell types showed the following changes in their frequency and distribution: (1) 5-HT, neurotensin and gastrin/CCK immunoreactive cells (i.c.) showed a decrease in frequency with age; (2) somatostatin i.c. frequency remained stable with age; (3) motilin, GIP, secretin and CCK i.c. showed a slight increase in frequency with age; (4) GLU/GLI and PYY i.c. decreased in frequency with age in the small intestine, caecum and proximal colon and an increase in frequency in the rectum. It was hypothesised that the endocrine cell types, whose presence and localisation is substantially stable in all examined ages, probably contain substances that are strictly necessary for intestinal function. In contrast the hormones contained in the cell populations that decreased with age, are probably involved in physiological needs during the milk and weaning diet or play a role in intestinal growth.     

Oral Loading with Propafenone: A Placebo-Controlled Study in Elderly and Nonelderly Patients with Recent Onset Atrial Fibrillation

The efficacy and safety of propafenone as an oral loading dose (600-mg single oral dose) in converting recent-onset atrial fibrillation (≤ 7 days duration) to sinus rhythm were evaluated in a single-blind, placebo-controlled study according to patients' age. Overall, 240 hospitalized patients, NYHA Class ≤ 2 without signs or symptoms of heart failure were enrolled: among patients aged ≤ 60 years, 55 were allocated to propafenone treatment and 59 to placebo, respectively, and among patients aged > 60 years, 64 were allocated to propafenone treatment and 62 to placebo, respectively. Results: In each age group, the likelihood of conversion to sinus rhythm was significantly greater after propafenone compared with plocebo at 3 and 8 hours. For patients aged ≤ 60 years, corresponding odd ratios were 3.78 (95% CI = 1.80–7.92, P = 0.04) at 3 hours and 4.74 (95% CI = 2.12–10.54, P = 0.02) at 8 hours; for patients aged > 60 years odd ratios were 5.03 (95% CI = 2.08–12.12, P = 0.02) at 3 hours and 6.75 (95% CI = 3.28–73.86, P = 0.01) at 8 hours, respectively. Logistic regression analysis showed that conversion to sinus rhythm within 3 hours was predicted by age ≤ 60 years (P = 0.0064) and by propafenone treatment (P < 0.0001), and conversion to sinus rhythm within 8 hours was predicted by age ≤ 60 years (P = 0.0467) and by propafenone treatment (P < 0.0001). The occurrence of adverse effects was observed in 14%-16% of propafenone treated patients and in 8% of placebo treated patients without significant differences according to age. In conclusion, in patients with recent-onset atrial fibrillation without signs of heart failure, propafenone as a single oral loading dose is effective. It is also effective in selected elderly subjects with a favorable safety profile. Moreover, spontaneous conversion to sinus rhythm appears to occur less frequently in elderly patients.