Biomedical subjects
Publications and source records attributed to Massimo Santini.
A case of a giant vegetation of the mitral valve causing sudden death of the patient is reported. The case underlines that urgent removal of a big mass must always be considered because of the risk of sudden death or catastrophic embolism. Echocardiographic differential diagnosis of a mass is discussed and is crucial for the choice of the strategy.
The aim of this study is to evaluate the heart rate adaptation obtained by a pacemaker, based on a measure of ventricular impedance in patients undergoing autonomic challenges. The evaluation procedure was based on the analysis of the mean value (MV) and heart rate variability (HRV) of RR and systolic pressure intervals, according to a set of neurovegetative stressors (controlled respiration in supine position and during active standing; mental stress; handgrip, and noninvasive sinusoidal stimulation of carotid baroreceptors). Each test lasted 5 minutes. Fifteen chronotropic incompetent patients first implanted, were studied three months after implantation. ECG, respiration activity, and noninvasive blood pressure were monitored. HRV was evaluated by spectral analysis. Variability in the low frequency (LF) and high frequency (HF) bands was compared by computing percentage and absolute powers. We found that baseline HR was 72.2 +/- 5.5 beats/min, in mental stress was 76.8 +/- 7.8 beats/min, in handgrip was 79.2 +/- 6.3 beats/min, and in active standing was 80.9 +/- 8.6 beats/min (P < 0.01, Friedman's test). During active standing, LF component was significantly higher with respect to baseline (25.7% of total power in standing; 9.4% in baseline, P < 0.01) and it was synchronous to the LF component of the arterial pressure variability. Carotid activation/deactivation by neck suction induced synchronous changes in the paced rates. In conclusion, closed loop strategy based on ventricular contractility continuously controls heart rate by tracking the sympathetic modulation to the heart.
INAMA, G., et al.: Far-Field R Wave Oversensing in Dual Chamber Pacemakers Designed for Atrial Arrhythmia Management: Effect of Pacing Site and Lead Tip to Ring Distance. The aim of the study was to determine the incidence and practical implications of far-field R wave oversensing (FFRWO) and its association with pacing site and lead tip to ring spacing (TTRS) in implantable devices designed to diagnose and treat atrial tachyarrhythmias and programmed with a fixed and short postventricular blanking period. The study included 395 patients who were implanted with a DDDRP pacemaker and prospectively followed. At implant and follow-up visits FFRWO was assessed by analyzing lead electrical measures and atrial tachyarrhythmic episodes collected in the device diagnostics. During a median follow-up of 12 months 11 (2.8%) of 395 patients showed a clinically significant FFRWO that induced inappropriate detection or pacemaker malfunctioning. The atrial pacing site of these 11 patients was right atrium appendage (RAA) for 3 patients, representing 1.1% of 254 RAA patients, coronary sinus ostium (CSO) for 7 patients, representing 7.4% of 94 CSO patients (P < 0.005 vs RAA), and lateral wall (LW) for 1 (2.9%) of 34 LW patients. The minimal value of the FFRWO to P wave ratio, measured at implant, associated with a clinically significant FFRWO was 0.6; therefore, a value of 0.5 was used as a cutoff to identify patients at risk of undesirable device behavior induced by FFRWO: there were 11 (9.6%) of 114 of RAA patients with short (< or = 10 mm) TTRS, 22 (18.8%) of 117 of RAA patients with long (> or = 17 mm) TTRS (P < 0.05 vs short TTRS), 21 (30.6%) of 64 of CSO patients short TTRS (P < 0.001 vs RAA patients with short TTRS) and 3 (30%) of 10 of CSO patients with long TTRS. The analysis showed that, despite the short postventricular blanking time, FFRWO inducing undesired functioning in AT500 pacemakers is infrequent (2.8% of patients). Compared to RAA, the CSO lead position was more frequently associated with FFRWO.TTRS < 10 mm was associated with lower risk of clinically significant FFRWO in RAA. (PACE 2004; 27:1221-1230).
BACKGROUND: The atrial Fibrillation/flutter Italian REgistry (FIRE) study was designed to obtain updated information regarding the clinical characteristics of and medical approach to patients requiring urgent medical care for atrial fibrillation (AF) or atrial flutter in a nationwide and representative series of hospitals. METHODS: 4570 consecutive patients admitted to the emergency room for AF/atrial flutter were enrolled in 207 hospitals. Of these, 2838 (61.9%) were hospitalized (median 6 days, 43% in cardiology and 57% in internal medicine departments), and constitute the population of this study. RESULTS: AF/atrial flutter represented 1.5% of all emergency room admissions and 3.3% of all hospitalizations. The mean age was 70 +/- 12 years; 89.9% had AF and 10.1% atrial flutter. In 31% of the hospitalized patients no cardiac disease was present, and in 18% no disease (either cardiac or non-cardiac) could be detected. Predictors of no attempt of cardioversion (37.5% of patients) included: onset of AF > 48 hours, heart failure, increasing age, syncope, admission to a non-cardiology department, stroke or transient ischemic attack (TIA). Predictors of in-hospital mortality (2.2%) included: age, heart failure, diabetes, admission to a non-cardiology department, and stroke or TIA. Predictors of the absence of sinus rhythm at discharge (35.6% of patients) included: no attempt of cardioversion, heart failure, chronic anticoagulation, AF duration > 48 hours, increasing age, stroke or TIA, and admission to a non-cardiology department. Transesophageal echocardiography was performed in only 6% of patients. CONCLUSIONS: AF/atrial flutter represent a significant burden on the health care system with a higher than expected hospitalization rate from the emergency room. One out of three discharged patients is not in sinus rhythm. There is still a wide gap between evidence-based medicine and real practice in the treatment of patients with AF.
The large amount of data accumulated in recent years has reinforced the idea that infectious agents may play a significant role in the pathogenesis of atherosclerosis and in the clinical manifestations of vascular disease. Seroepidemiological and experimental data linking Herpesviridae and Chlamydia pneumoniae to atherosclerosis appear to be confirmed by a number of studies, while the available evidence regarding Helicobacter pylori is more conflicting, partly due to the fact that the interest in this agent is more recent. Infectious agents may influence atherogenesis through a number of mechanisms, ranging from cell lysis to the stimulation of adhesion molecule expression and cytokine production by infected cells. The development of atherosclerosis after an acute infection seems unlikely. Rather, it appears that a chronic, persistent form of infection, especially with Chlamydia pneumoniae, may favor those structural and proinflammatory changes in the vascular wall which are necessary for the formation of an atheroma. A persistent chlamydial infection is accompanied by an increased production of microbial heat shock protein 60, which may induce antigenic mimicry and a chronic inflammatory reaction in the vascular wall. Pharmacological trials have yielded conflicting indications regarding the hypothesis that treatment with macrolide antibiotics may limit the progression of vascular disease and the recurrence of cardiovascular events, although in a limited number of cases. However, antimicrobial drugs do not act specifically against a single infectious agent and more specific therapeutic agents would be needed in order to test a causative link between a single infectious agent and vascular disease.
A small non-quantified number of patients is reported to be affected by forms of angina pectoris already treated by traditional therapy but no longer able to achieve better results by drugs or surgery: this is called "refractory angina". Treatments like external counterpulsation, transmyocardial laser revascularization, stem cell transplantation or spinal cord stimulation may be suitable for these patients. The analysis of major studies on spinal cord stimulation based on exercise ECG, Holter monitoring and positron emission tomography, has shown a reduction in anginal attacks and in nitroglycerin pills. Though in small figures, an improved perfusion of the ischemic areas, an increase in the time of ischemia and cardiac mortality comparable to bypass surgery as well as a better quality of life and lower costs with respect to traditional treatment are also evident. Patients who are at high risk of mortality for bypass surgery, and who cannot receive significant benefits from revascularization or improved pharmacological therapy are candidate to spinal cord stimulation. Spinal cord stimulation is safe and effective in about 70% of patients. Some issues have not been investigated yet: the clinical characteristics of "non-responders" and the possibility of avoiding sudden cardiac death in stimulated patients.
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Cardiac resynchronization therapy is a novel nonpharmacologic approach to treating patients who have advanced heart failure with left bundle branch block (LBBB). Such a therapy is based on the original theory that synchronous biventricular pacing is able to reduce the interventricular delay caused by LBBB in patients with heart failure. Although there is convincing evidence that biventricular pacing increases the left ventricular ejection fraction, decreases mitral regurgitation, and improves symptoms caused by heart failure, the percentage of nonresponders to such therapy has been described as high as about one third of patients with heart failure having LBBB. Factors responsible for this relatively high prevalence are reviewed, the most important of them probably being left intraventricular dyssynchrony, which can persist after biventricular pacing, notwithstanding right and left interventricular resynchronization. Such a dyssynchrony, as evaluated by tissue Doppler imaging, may be because of the discordance between the site of the left ventricular pacing and the site of the left ventricular delay. Therefore, to characterize the pathophysiologic pattern of LBBB, the investigators suggest an assessment of the electromechanical dysfunction with a noninvasive reliable technique, such as tissue Doppler imaging, which can be repeated after biventricular pacing.
The treatment of patients with angina pectoris refractory to medical therapy and unsuitable for revascularization procedures has yet not been well standardized. Previous retrospective studies and small prospective studies have suggested beneficial effects of spinal cord stimulation (SCS) in these patients. We created a Prospective Italian Registry of SCS to evaluate the short- and long-term clinical outcome of patients who underwent SCS device implantation because of severe refractory angina pectoris. Overall, 104 patients were enrolled in the registry (70 men, aged 68 +/- 17 years), most of whom (83%) had severe coronary artery disease. Average follow-up was 13.2 +/- 8 months. Overall, 17 patients (16%) died, 8 (8%) due to cardiac death. Among clinical variables, only age was found to be significantly associated both with total mortality (p = 0.04) and cardiac mortality (p = 0.02) on Cox regression analysis. A significant improvement of anginal symptoms (> or =50% reduction of weekly anginal episodes, compared with baseline) occurred in 73% of patients, and Canadian Cardiovascular Society angina class improved by > or =1 class in 80% and by > or =2 classes in 42% of patients, with a relevant reduction in the rate of hospital admission and days spent in the hospital because of angina (p <0.0001 for both). No life-threatening or clinically serious complications were observed. The most frequent side effect consisted of superficial infections, either at the site of puncture of electrode insertion or of the abdominal pocket, which occurred in 6 patients. In conclusion, our prospective data point out that SCS can be performed safely and is associated with a sustained improvement of anginal symptoms in a relevant number of patients with refractory stable angina pectoris.
AIMS: Aim of the present study was the development and the subsequent validation of a simple risk classification system for patients presenting with syncope to the emergency departments. METHODS AND RESULTS: A group of 270 consecutive patients (145 females, mean age 59.5 years) presenting with syncope to the emergency departments of six community hospitals of the Lazio region of Italy was used as a derivation cohort for the development of the risk classification system. Data from the baseline clinical history, physical examination and electrocardiogram were used to identify independent predictors of total mortality within the first 12 months after the initial evaluation. Multivariate analysis allowed the recognition of the following predictors of mortality: (1) age >65 years; (2) cardiovascular disease in clinical history; (3) syncope without prodromes; and (4) abnormal electrocardiogram. The OESIL (Osservatorio Epidemiologico sulla Sincope nel Lazio) score was calculated by the simple arithmetic sum of the number of predictors present in every single patient. Mortality increased significantly as the score increased in the derivation cohort (0% for a score of 0, 0.8% for 1 point; 19.6% for 2 points; 34.7% for 3 points; 57.1% for 4 points; p<0,0001 for trend). A similar pattern of increasing mortality with increasing score was prospectively confirmed in a second validation cohort of 328 consecutive patients (178 females; mean age, 57.5 years). CONCLUSIONS: Clinical and electrocardiographic data available at presentation to the emergency department can be used for the risk stratification of patients with syncope. The OESIL risk score may represent a simple prognostication tool that could be usefully employed for the triage and management of patients with syncope in emergency departments.
AIM OF THE STUDY: To evaluate the effectiveness of Ibutilide in cardioversion of persistent atrial fibrillation in patients with sinus node disease wearing a dual chamber pacemaker and to assess the potential role of overdrive ventricular pacing in prevention of drug related proarrhythmia. METHODS AND RESULTS: Fifty-three sinus node disease patients (35 males; mean age 75 +/- 9.5 years), implanted with a dual chamber pacing system, with persistent atrial fibrillation, lasting for 328 +/- 416 days, received 1-2 mg of intravenous Ibutilide. Pacing mode was programmed in VVI at 90 ppm, in order to suppress spontaneous ventricular activity. All patients were monitored for 4 hours. Late occurrence of ventricular arrhythmias was evaluated using the pacemaker memory. Ventricular pacing threshold, spontaneous electrogram amplitude and pacing impedance were measured before and after Ibutilide infusion. Cardioversion to sinus rhythm occurred in twenty-two patients (41.5%). Treatment success was significantly related to shorter atrial fibrillation duration. Paced QT interval duration increased from 412 +/- 36 ms to 481 +/- 40 ms (p < 0.0001), without differences between responders and non responders; QRS width did not change significantly (from 152 +/- 25 ms to 161 +/- 25 ms; p = n.s.). No early or late episodes of sustained or non sustained polymorphic ventricular tachycardia were observed. Pacing and sensing threshold did not show any significant variation. CONCLUSIONS: Ibutilide showed a good effectiveness in treating persistent atrial fibrillation in paced patients. Overdrive ventricular pacing may have played a role in preventing drug induced ventricular proarrhythmia. No adverse effect on pacing threshold was observed.
Dual defibrillator implantation represents an emerging option to treat patients with drug refractory atrial fibrillation. Atrial antitachycardia pacing and cardioversion have been demonstrated to be highly effective in treating spontaneous tachyarrhythmias and may reduce atrial fibrillation burden by preventing atrial remodeling. Device implantation has been associated to improved quality of life and reduced hospitalization rate. Patient selection and tailored device programming are critical as regard to clinical outcome. Individual psychological profile analysis as well as underlying heart disease and atrial fibrillation clinical patterns represent the main drivers for the right strategy. Controlled studies are needed in order to define the subset of patients who can benefit more from device implantation.
In patients with conventional indication for ICD implantation, atrial fibrillation may occur in more than 50% during the life-span of the device and may lead to severe adverse events. Dual chamber defibrillators with atrial antitachycardia functions, including prevention algorithms, arrhythmia detection capability and atrial therapy options (antitachy pacing and cardioversion) have been recently introduced. The aim of this review is to examine the effectiveness of these new devices and to identify patients who may benefit. We recently studied 112 patients who received the device because of life-threatening ventricular arrhythmias. Fifty-five percent of them had atrial fibrillation prior to implantation. During the follow-up (one year on average), 27% had at least one episode of sustained atrial tachyarrhythmia. Effectiveness of atrial antitachy pacing was 71% on regular atrial tachycardia and 36% on irregular atrial tachyarrhythmias. Atrial shock efficacy was over 90% when adequately programmed. Interestingly, near half of the episodes started as regular atrial tachycardia and accelerated and became less organized in few minutes. Early delivery of antitachy pacing may increase success rate and decrease the need for atrial shock. Furthermore, it may prevent atrial remodeling and reduce atrial fibrillation burden. Based on our experience, we recommend that all patients with a class I indication for defibrillator implantation (related to risk of ventricular arrhythmias) who have a history of or are at risk of developing atrial tachyarrhythmias should receive a dual chamber defibrillator equipped with atrial antitachycardia functions. Furthermore, patients either with a history of heart failure, with poor functional capacity (functional class III or IV), depressed left ventricular ejection fraction, a need for monitoring of atrial rhythm, or in whom there is some concern about appropriate detection of ventricular arrhythmias, may benefit from a single device capable of managing ventricular and supraventricular arrhythmias.
Atrioventricular nodal reentrant tachycardia (AVNRT) is one of the most common regular narrow QRS tachycardias. Although the principal understanding of the physiology of dual atrioventricular conduction as a substrate for the reentry mechanism in AVNRT has not changed during the last 25 years, there is still some uncertainty with regard to the exact circuit delineation. At least four forms of AVNRT have been described and several possible circuits have been proposed. Although the refinement of our knowledge about AVNRT seems to be purely academic since further insight will probably not increase the success rate of treatment by radiofrequency catheter ablation, AVNRT continues to puzzle both clinical and basic electrophysiologists. The authors summarize our present knowledge about AVNRT and stress the unique features of the atrioventricular junction anatomy and the current opinions on the reentrant impulse propagation.
BACKGROUND: The relation between repolarization and refractoriness has been clinically evaluated both in the atrium and ventricle. However, this relation has not been carefully investigated in the atria of patients with persistent atrial fibrillation after cardioversion. METHODS: We determined the refractoriness and monophasic action potential duration at 90% of repolarization (MAP90), at 5 pacing cycle lengths (300 to 700 ms) and in 5 right atrial sites after internal cardioversion of persistent atrial fibrillation in 27 patients. RESULTS: The effective refractory periods (ERPs) were longer in amiodarone-treated patients (group 1) than in wash-out patients (group 2) (211.3 +/- 26.4 vs 199.1 +/- 24.3 ms, p < 0.002) as well as the MAP90 (243.6 +/- 36.8 vs 223.1 +/- 29.2 ms, p < 0.001). Linear regression analysis showed a direct relation between the MAP90 and ERP changes induced by different pacing cycle lengths (r = 0.77 and r = 0.92 in the amiodarone and wash-out patients, respectively). The ERP/MAP90 ratio was similar at all pacing cycle lengths in both wash-out and amiodarone groups and was always < 1. The mean ERP and MAP90 were shorter in the lateral right atrial sites than in the atrial roof and septum in both group 1 and group 2 patients (p < 0.001). CONCLUSIONS: A linear correlation was found between ERP and MAP90 in response to changes in pacing cycle lengths. Postrepolarization refractoriness was not observed after cardioversion of persistent atrial fibrillation. Pretreatment with oral amiodarone does not affect these electrophysiological features or the dispersion of ERP and MAP90 in the right atrium after sinus rhythm restoration.
BACKGROUND: Low-energy internal cardioversion (LEIC) is a safe and effective procedure for the restoration of sinus rhythm in patients with atrial fibrillation refractory to external cardioversion. However, the procedure needs fluoroscopy and the use of the electrophysiology laboratory, even when the esophageal approach is utilized. The aim of this study was to assess the efficacy, safety and tolerability of a new simplified procedure of esophageal LEIC performed without fluoroscopy, outside the electrophysiology laboratory. METHODS: Thirty consecutive patients (23 males, 7 females) with persistent atrial fibrillation were submitted to LEIC using a step-up protocol (by steps of 50 V, starting from 200 V). Twenty (66%) were resistant to external cardioversion. A large surface area lead (cathode) was positioned within the esophagus, 45 cm from the nasal orifice. A second large surface area lead (anode) was positioned in the right atrium via the right internal jugular vein without fluoroscopic control. Synchronization of delivery of the shock with the QRS was achieved by means of two cutaneous electrodes positioned on the thoracic wall. RESULTS: Sinus rhythm was restored in 28 patients (93%) with a mean delivered energy of 15.2 +/- 7.5 J (range 5-27 J) and a mean impedance of 48.3 +/- 5.6 Ohm. No complication occurred during and after the procedure that was well tolerated under sedation. CONCLUSIONS: This new technique of performing esophageal LEIC is effective and seems to be safe and well tolerated. In this way internal cardioversion can be performed without fluoroscopy, outside the electrophysiology laboratory.
The term atrial flutter was introduced 90 years ago for an arrhythmia with a unique electrocardiographic pattern. The development of endocardial mapping techniques in the last decade allowed the detailed characterization of the tachycardia circuit and the identification of the cavotricuspid isthmus as its critical part. This review stresses the position of atrial flutter in the new classification of atrial tachycardias and focuses on its unique electrophysiological characteristics and different variants described in humans. Transcatheter radiofrequency ablation across the cavotricuspid isthmus constitutes a feasible and safe therapy, which prevents flutter recurrences during the long-term follow-up. This paper describes the different techniques that validate bidirectional isthmus block, which is an important endpoint for successful ablation.
In the last few years many studies have been performed with the aim of gaining a better understanding of the pathophysiological nature of atrial fibrillation. These recent observations provide new insights into the initiation and perpetuation of atrial fibrillation, underlying the importance of the pulmonary veins as major sources of atrial triggers and introducing new concepts such as the atrial electrical remodeling and the spatial heterogeneity of the electrophysiological characteristics of this arrhythmia. The increasing knowledge about the cardiac ion channel structure and function and about the electrophysiological actions of the antiarrhythmic drugs may contribute to a better comprehension of the mechanisms of the pharmacological termination of the arrhythmia. In part I of the review we try to give a unified vision of the old models and new concepts about the molecular and ionic fundamentals of antiarrhythmic drug actions.