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Sir,—In a recent article, Biffi et al concluded that treatment guided by head up tilting is a reliable method of treating severely symptomatic and high risk patients with malignant vasovagal syndrome.1 They also found metoprolol to be superior to clonidine treatment according to their protocol. Their “pharmacological test” comprised isoprenaline infusion in five progressive steps, from 1–5 μg/min at 80° head up tilt. The specificity of isoprenaline challenge with steep angles of head up testing has been questioned. Natale et al investigated the effects of both differing degrees of head up tilt and progressive rates of isoprenaline infusion in normal volunteers with no history of syncope or presyncope.2 Testing at a 70° angle with a low dose isoprenaline infusion provided an adequate specificity of 88%, this fell to 60% during 80° head up testing. Limiting test duration at 80° to 10 minutes would have reduced the false positive rate to 16%. Furthermore, increasing the dose of isoprenaline to …

Nowadays, technological progress has equipped clinicians with new useful devices for the collection, analysis and presentation of data. As a consequence, many diseases and pathological conditions have been studied in a more detailed way, sometimes with remarkable results. In fact, they are not always validated by the old physiological models. In this respect, we present the case of low gradient severe aortic stenosis, a condition characterised by a small aortic valve area and a low-pressure gradient. According to the mathematical and physical assumptions these readings are contradictory whereas the Doppler-echocardiography shows clearly the existence of such a situation. In this work, we have described the physiological base of this phenomenon and discussed the limitations of the technology used. In this work, we are going to analyse some conditions commonly observed in daily clinical practice in order to prompt a critical outlook in both clinicians and technicians about the instrumentations used and the methods applied.

Monitoring sphincter activity presents remarkable methodological and conceptual problems. The particular shape, structure and function of the sphincters require an accurate analysis of the objectives of diagnostic procedures and the physical concepts applied. Researchers have developed practical solutions to the description of the sphincter activity not always rigorous on a theoretical basis, and the measurement results are difficult to evaluate and compare, in the event that the contour conditions of the assumed descriptive model are not well defined. A practical solution is to "create" a constant curvature radius chamber by introducing a cylinder within the sphincter and measuring the pressure, linearly proportional to the tangential force strength of the wall. This paper analyzes the coherence between the theoretical basis and the practical solutions of the different methods of sphincter monitoring, to clarify some controversial aspects, highlight the limitations and to suggest possible alternative solutions.

This study tested the hypothesis that venular resistance increases during ischaemia and that a prevalent nitrates-induced venodilationis the cruc a mechanism underlying their ability to relieve ischaemia. Using the model of postreactive hyperaemia we used mercuryin-rubber surain gauges to measure forearm blood flow (FBF) and forearm circumference (FC) before and after 5 mg sublingual isosorbide dinitrate in twelve healthy volunteers. The FC change during reactive hyperaemia was evaluated according to a hydraulic model which assumes that arteriolar resistance (AR) controls the blood inflow and that venular resistance (VR) controls the blood outflow of the vascular capillary reservoir. In this setting FC represents the reservoir volume and any change in this parameter represents the instantaneous difference between input and output flows. In the absence of nitrates and five minutes of arterial closure, the hyperaemic FC curve shows a rapid increase followed by a slow recovery demonstrating a rapid inflow followed by a delayed outflow of the reservoir. This behaviour may be explained by assuming an initial very low arterial resistance and high venular resistance, followed by a slow requilibrium of the two. Repeating the experiment after nitrates intake, the hyperaemic FC curve shows a reduced dimension and a faster recovery to the baseline. Compared with the previous condition, this finding may be explained by assuming a reduced initial venular resistance, which facilitates the blood outflow and hence muscle perfusion. Our findings are coherent with an ischaemia-induced arteriolar dilatation which facilitates filling, and a simultaneous venular constriction which opposes emptying (arteriovenous ischaemic mismatch): the action of the nitrates seems to restore the mismatch by acting on the venous side.

Various modalities of cardiac pacing have been proposed in the past to improve hemodynamics, either directly or indirectly. Some of these are conventional ways of cardiac stimulation, others such as biventricular or left ventricular pacing, represent dedicated pacing techniques. Left ventricular and biventricular pacing are successfully applied in those patients with congestive heart failure who have conduction disturbances (i.e. left bundle branch block) as they correct the ensuing intra- and interventricular dyssynchrony. This is the reason why these pacing modalities are described as cardiac resynchronization therapy. According to the results of a series of studies, the cardiac resynchronization therapy seems to have a favourable clinical impact in terms of quality of life, morbidity and hospitalization rate. On-going and future studies should assess the impact of resynchronization therapy on overall mortality and its cost-effectiveness profile in specific subgroups of patients. Other open issues regard (i) the convenience of using biventricular pacing as a pacing-alone therapy or in combination with ventricular defibrillation capability, especially for potential candidates to heart transplantation, and (ii) the ways to identify properly the responders to resynchronization therapy.

This study analyzed the relations and time-related changes in eligibility for cardiac resynchronization therapy and prophylactic defibrillator implantation in 161 potential candidates for heart transplantation. Although up to 62% of patients who fulfilled the severity criteria for heart transplantation were eligible for either device, this percentage increased as clinical/instrumental parameters of heart failure severity worsened.

Aim: Minimization of X-ray exposure remains a primary issue in cardiac electrophysiology. The effectiveness of X-ray beam filtration during cardiac electrophysiological procedures was therefore studied, using a 0.05-mm-thick tantalum (Ta) foil, as a filter on the primary X-ray beam, to reduce the patient dose without degradation of image quality. Method: Preliminary tests were made on a phantom developed with polymethylmethacrylate, catheters, and guide wires. The filter was then used in patients during cardiac procedures. Identical patient images were obtained with and without the Tafilter insertion and the ratio between image quality and patient dose was evaluated. Changes in patient dose and signal-to-noise ratio, as image quality index were measured on the phantom and in patients. Results and Conclusions: When the Ta filter was used, the mean effective individual patient dose decreased by 3 to 40% (mean reduction = 27%), with no perceivable difference in image quality estimated by electrophysiologists. This Ta filter may be useful to limit the radiation exposure of patients and operators during cardiac procedures. (PACE 2009; 32:S109‐S112)

We investigated frequency/characteristics of acute coronary syndrome-like (ACS-like) electrocardiographic (ECG) profiles among patients with a final diagnosis of acute aortic syndrome (AAS), and explored pathophysiologic determinants and prognostic relevance within each Stanford subtype. We blindly reviewed presentation electrocardiograms of 233 consecutive patients with final diagnosis of AAS (164 Stanford type A) at a regional treatment center. Prevalence of ACS-like ECG findings was 27% (type A, 26%, type B, 29%); most were non–ST-elevation myocardial infarction-like. Patients with ACS-like ECG findings more often had coronary ostia involvement (p = 0.002), pleural effusion (p = 0.02), significant aortic regurgitation (p = 0.01), and troponin positivity (p = 0.001). ACS-like ECG profile in type A disease was independently associated with coronary ostia involvement (odds ratio [OR] 5.27, 95% confidence interval [CI] 1.75 to 15.88). ACS-like ECG profile predicted in-hospital mortality (OR 2.90, 95% CI 1.24 to 6.12), as did age (each incremental 10-year: OR 1.59, 95% CI 1.14 to 2.22), and syncope at presentation (OR 2.90, 95% CI 1.16 to 7.24). In conclusion, about 25% of our AAS patients (in either Stanford subtype) presented ACS-like ECG patterns—often with non–ST-elevation myocardial infarction characteristics—which could cause misdiagnosis. ACS-like ECG profile was associated with more complicated disease, and in type A disease was a strong independent predictor of in-hospital mortality.

Marfan Syndrome and Bicuspid Aortic Valve (BAV) are characterized by the congenital/inherited alteration of the fibrillin proteins of aortic wall extracellular matrix, with higher incidence of aortic dissection/rupture even without aortic dilation. Therefore, early identification and treatment of aortic involvement could improve prognosis. The purpose of this study was to evaluate aortic elastic properties of BAV and Marfan Syndrome patients to identify an index of early aortic involvement. Methods: A Magnetic Resonance Imaging (MRI) study was performed on 38 BAV patients, 20 Marfan patients and 14 healthy volunteers as a control group. A high-resolution gradient-echo sequence was applied in the axial plane at the level of pulmonary artery bifurcation to evaluate aortic distensibility. Results: Aortic distensibility was significantly different among the three groups (ANOVA, p = 0.0001) and was sensibly reduced in BAV (0.0056 ± 0.0048 versus 0.025 ± 0.006 control group) and Marfan (0.0085 ± 0.006 versus 0.025 ± 0.006 control group). Intraobserver and interobserver reproducibility for diastolic measurements were 1.2% and 0.4% respectively and for systolic measurements, they were 1.1% and 0.3% respectively. Conclusion: In BAV or Marfan Syndrome patients, MRI evaluation of abnormal distensibility may provide a reliable index of early aortic involvement, even before aortic dilation occurs.

Background P wave dispersion has been previously suggested as a potential tool for predicting the risk of recurrence of atrial fibrillation after electrical cardioversion. We investigated whether different P wave dispersion values are associated with recurrence of atrial fibrillation in the short (≤1 month after cardioversion) and longer term. Methods In 37 patients with long-lasting persistent atrial fibrillation (mean duration 21±36 months) with ( n =19) or without ( n =18) amiodarone pretreatment as antiarrhythmic prophylaxis, maximum and minimum P wave duration and P wave dispersion were measured 1 min after internal cardioversion. Results P wave dispersion was lower in patients with amiodarone pretreatment (28.3±9.5 vs. 21.9±7.3 ms, P =0.029). The subgroups of patients with recurrence of atrial fibrillation at 1 month or in the long-term did not differ from the rest of the study sample regarding age, sex, atrial fibrillation duration, left atrial dimensions or ejection fraction. P wave dispersion was significantly higher in patients with short-term atrial fibrillation recurrence (≤1 month) than in the rest of the population. Furthermore, P wave dispersion values >25 ms were associated with a higher short-term relapse rate. No significant relation was present in the long-term. Conclusions Our results suggest that P wave dispersion analysis immediately after internal cardioversion may help predict short-term recurrences of atrial fibrillation. These findings may be related to different mechanisms and predisposing factors for short-term and late recurrences. The long-term predictive value of serial evaluations of P wave dispersion during follow-up deserves investigation.

The effects of atrial internal cardioversion on QT interval and QT dispersion (parameters associated with increased risk of ventricular tachyarrhythmias) are unknown. We investigated changes in QT interval, QTc and QT dispersion immediately after shock delivery for internal cardioversion in patients with chronic persistent atrial fibrillation.Twenty-two patients with chronic persistent atrial fibrillation (mean duration, 17+/-23 months) underwent transvenous low-energy internal atrial cardioversion with a step-up protocol of shocks delivered between catheters in the right atrium and coronary sinus. (successful shock, 7.2+/-4.2 J). RR interval, QT interval, QTc interval, QT dispersion, and QTc dispersion were all measured on three consecutive beats (at 75 mm/s on at least 9 of 12 leads) and then averaged both before and after (1) the last unsuccessful shock, and (2) sinus rhythm restoration.All parameters remained similar in the minute before and after the last unsuccessful shock. At 1 min after the successful shock, abrupt increases in QT dispersion (+43.8% vs. pre-shock; P0.001 at least significant difference analysis) and QTc dispersion (+30.0%; P0.05) were observed, followed by a gradual return to pre-shock values at 15 min.These findings strongly suggest the likely existence of a brief period of increased electrical vulnerability immediately after restoration of sinus rhythm by internal cardioversion. Particular caution should therefore be applied whenever class III antiarrhythmic drugs are administered immediately after successful internal atrial cardioversion.

Internal cardioversion can restore sinus rhythm with energies below 6–10 J, often without anaesthesia/sedation. We investigated its safety and short-/medium-term efficacy in patients with persistent atrial fibrillation (AF) with left ventricular dysfunction (defined as ejection fraction ≤40%). Among 34 patients with persistent AF who agreed to receive internal cardioversion, 16 had left ventricular dysfunction and 18 did not (the groups were similar as regards age, duration of AF and pretreatment with amiodarone). Internal CV was performed delivering 3.0/3.0-ms biphasic shocks between coil catheters using a step-up protocol. Sinus rhythm was always restored. General anaesthesia (administered only when discomfort was not tolerated) was required only in 2 of the 16 (12.5%) patients with left ventricular dysfunction. The defibrillation threshold was similar in patients with and without left ventricular dysfunction (10.2±6.9 vs. 8.4±4.9 J; p =0.37). Short-term (within 72 h) AF recurrence rates in the presence and absence of left ventricular dysfunction were 19% (3/16) and 6% (1/18), respectively ( p =0.51). After cardioversion, all patients received antiarrhythmic drugs (mostly amiodarone in patients with left ventricular dysfunction and class IC agents in the remainder). With mean follow-up periods of about 220 days, AF recurrence rates among patients with and without left ventricular dysfunction were 50% (8/16) and 28% (5/18), respectively ( p =0.328). We conclude that even in patients with left ventricular dysfunction, internal CV is safe and effective, minimizing risks from anaesthesia. Although these patients may have a higher risk of short- or medium-term AF recurrence, 6-month maintenance of sinus rhythm is possible in about 50% of cases.

De. brillation Threshold in Chronic and Reinduced AF.Introduction: Induced versus spontaneous atrial fibrillation (AF) is of interest for assessing atrial defibrillation threshold reproducibility. Methods and Results: Twenty-one patients with chronic AF underwent internal cardioversion with assessment of atrial defibrillation threshold at baseline and at reinduced AF. High right atrial (HRA) and coronary sinus (CS) bipolar recordings were analyzed to measure the mean local atrial period, its coefficient of variation, the 5th (P5) and 95th (P95) percentiles of atrial intervals, and the percentage of points lying at the baseline (number of occurrences), and to quantify AF organization. Atrial defibrillation threshold was comparable in baseline and reinduced AF in terms of leading-edge voltage and delivered energy. Baseline and reinduced AF were comparable with regard to overall signal parameters (both in HRA and CS) and the presence of an organized arrhythmia pattern. As for individual variables, P5 increased while P95 and coefficient of variation decreased in reinduced AF compared with spontaneous AF (statistical significance was achieved for all these parameters in HRA, but only for coefficient of variation and P95 in CS). Conclusion: Sustained AF reinduced after cardioversion of chronic AF is comparable with baseline AF in terms of atrial defibrillation threshold, atrial cycle length, and pattern of organization. Therefore, a clinical model based on reinduction of sustained AF after cardioversion is suitable for studying the effects of a series of interventions on atrial defibrillation threshold. However, because this model does not yield a form of AF with comparable indices of local refractoriness (e.g., P5), it is not recommended when analyzing local electrophysiologic properties.