The Whereabouts of an Ancient Wanderer: Global Phylogeography of the Solitary Ascidian Styela plicata

Genetic tools have greatly aided in tracing the sources and colonization history of introduced species. However, recurrent introductions and repeated shuffling of populations may have blurred some of the genetic signals left by ancient introductions. Styela plicata is a solitary ascidian distributed worldwide. Although its origin remains unclear, this species is believed to have spread worldwide by travelling on ship's hulls. The goals of this study were to infer the genetic structure and global phylogeography of S. plicata and to look for present-day and historical genetic patterns. Two genetic markers were used: a fragment of the mitochondrial gene Cytochrome Oxidase subunit I (COI) and a fragment of the nuclear gene Adenine Nucleotide Transporter/ADP-ATP Translocase (ANT). A total of 368 individuals for COI and 315 for ANT were sequenced from 17 locations worldwide. The levels of gene diversity were moderate for COI to high for ANT. The Mediterranean populations showed the least diversity and allelic richness for both markers, while the Indian, Atlantic and Pacific Oceans had the highest gene and nucleotide diversities. Network and phylogenetic analyses with COI and ANT revealed two groups of alleles separated by 15 and 4 mutational steps, respectively. The existence of different lineages suggested an ancient population split. However, the geographic distributions of these groups did not show any consistent pattern, indicating different phylogeographic histories for each gene. Genetic divergence was significant for many population-pairs irrespective of the geographic distance among them. Stochastic introduction events are reflected in the uneven distribution of COI and ANT allele frequencies and groups among many populations. Our results confirmed that S. plicata has been present in all studied oceans for a long time, and that recurrent colonization events and occasional shuffling among populations have determined the actual genetic structure of this species

Contribution of decreased atrial function in the pathogenesis of neurally mediated syncope.

One of the most important mechanisms proposed in the pathogenesis of neurally mediated syncope considers the stimulation of myocardial mechanoreceptors as the final trigger leading to reflex hypotension and bradycardia. The aim of our study was to analyze the modifications of systolic and diastolic velocities of the left ventricle by tissue Doppler echocardiography, during the upright tilt test, to confirm the presence of an increased ventricular contractility before syncope. We evaluated 47 patients (mean age 43 years) with unexplained syncope and 13 healthy subjects. Three echocardiographic recordings were collected: at baseline, during the initial 5 minutes of the test, and after 15 minutes of tilt. The upright tilt test was positive in 28 patients. During the test, all of them had a similar, significant, progressive reduction of left ventricular end-diastolic volume, left atrial area, and left atrial volume. In contrast, the left ventricular ejection fraction showed an early, more pronounced decrease in those with positive tests. By tissue Doppler echocardiography, the systolic waves remained almost unchanged, and the early filling waves decreased similarly in those with positive or negative findings and the controls. In contrast, the atrial filling waves showed a significant decrease only in patients with positive tests. In conclusion, our study did not find increased ventricular contractility before syncope. In contrast, a decreased atrial contribution to ventricular filling characterized patients with positive upright tilt test results, which, we postulate, may be an important contributory factor to vasovagal syncope

Long-term follow-up of the signal-averaged ECG in arrhythmogenic right ventricular cardiomyopathy: correlation with arrhythmic events and echocardiographic findings

AIMS: The aims of our study were to evaluate late potential changes during long-term follow-up in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) and to correlate these results with echocardiographic findings and sustained ventricular tachycardia (VT) occurrence. METHODS AND RESULTS: We studied 31 patients (22 males and 9 females; mean age 29+/-16) during 8 years of follow-up by signal-averaged ECG (SAECG) and echocardiography. Ten subjects experienced episodes of sustained VT. During follow-up, all the SAECG parameters showed a progressive significant increase in late potentials. In contrast, echocardiographic indices did not show evidence of relevant modifications. Patients with sustained VT were characterized by significantly lower left and right ventricular ejection fractions, longer values of filtered QRS at 25/40/80-250 Hz filters, and longer high-frequency low-amplitude (HFLA) signals at 25-250 Hz at baseline. The analysis of SAECG modification during follow-up indicated that only HFLA signals at 25-250 Hz increased significantly in the sustained VT group. CONCLUSION: We detected a progressive increase in delayed ventricular conduction by SAECG not associated with significant echocardiographic changes. Therefore, the conduction disturbance seems to increase independently from anatomical alterations. The baseline SAECG and echocardiographic parameters, more than their modifications during follow-up, appear to be useful in identifying patients with sustained VT

AUTONOMIC PROFILE AND ARRHYTHMIC RISK STRATIFICATION AFTER SURGICAL REPAIR OF TETRALOGY OF FALLOT.

BACKGROUND: Severe ventricular arrhythmias represent one of the main causes of mortality after repair of tetralogy of Fallot. Their appearance is primarily caused by the large ventricular scar created by surgical intervention. However, the role of autonomic activity as a modulating factor should be considered. The aim of our study was to evaluate this activity in a low-risk group of patients operated on for TOF and its correlation with the occurrence of sustained ventricular tachycardia. METHODS AND RESULTS: The study group included 38 patients with a mean age of 31 +/- 10 years, selected out of 76 subjects operated on for total correction of tetralogy of Fallot. After a mean interval of 21.9 +/- 6 years from surgical procedure, they underwent electrocardiography, echocardiography, and time domain heart rate variability (HRV) analysis obtained by 24-hour Holter monitoring. Thirty-five healthy subjects comprised the control group for HRV analysis. During a mean follow-up of 6.2 +/- 3 years, 8 patients experienced episodes of sustained ventricular tachycardia. Among different HRV parameters, the standard deviation of all normal beat intervals showed a significant reduction in this group of patients (91.7 +/- 19 versus 133.4 +/- 46, P < .02). Echocardiographic examination demonstrated an increased left ventricular end diastolic volume (85.6 +/- 55 versus 61.3 +/- 13 mL/m(2), P < .05) and a reduced left ventricle ejection fraction (53.9 +/- 9 versus 61.0 +/- 6 %, P < .01) in arrhythmic patients. QRS duration was similar in patients with or without sustained ventricular tachycardia. CONCLUSIONS: Patients after surgical correction of tetralogy of Fallot, considered to be at low risk, showed a significant incidence of severe ventricular arrhythmias. HRV analysis seems to be a useful method for identifying arrhythmic patients, and the standard deviation of all normal beat intervals appears to be the more helpful index

Age-related hemodynamic changes during vasovagal syncope

Objective The aim of our study was to identify specific age-related hemodynamic changes during upright tilt test in patients with vasovagal syncope. Methods We studied 115 subjects who were referred to us for unexplained syncope during 65\ub0 tilt with pharmacological challenge (s.l. nitrate) by noninvasive monitoring of blood pressure (Finometer). Two derived variables were also considered: total peripheral resistance and stroke volume. The patients were divided into 3 groups by age: Group 1, 10\u201330 yrs; Group 2, 31\u201350 yrs; and Group 3, > 51 yrs. Results The test was positive in 65 patients (57%). During the first 20 min of the test, older patients experienced lower increases in heart rate (p < 0.00001) and premature reduction of total peripheral resistance (p < 0.005) and systolic blood pressure (p < 0.005). Group 1 showed more pronounced decreases in stroke volume (p < 0.01). No differences emerged between negative and positive patients. In the 5 min that preceded syncope, younger subjects experienced a distinct, transient increase in heart rate immediately before symptom onset (p < 0.005). Blood pressure was prematurely and progressively decreased in Group 3, whereas it decreased only in the 90 s prior to syncope in Groups 1 and 2 (p < 0.01). Conclusions Our results suggest that blunted sympathetic activation occurs during passive orthostatism in older patients. On the other hand, hemodynamic changes before symptom onset seem to indicate as in younger subjects syncope results from an excessive sympathovagal reaction, whereas in older subjects it is related to an overwhelming, progressive central vagal activity that is associated with a defective peripheral sympathetic activation