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Biomedical subjects

G Critelli

Publications and source records attributed to G Critelli.

At least 37 records · Page 2Linked to original sources
PubMed1991

[The transcatheter ablation of arrhythmias].

The introduction of transcatheter ablation techniques has opened a new era of the management of tachyarrhythmias. The rationale of these therapeutic procedures lies in the induction of an irreversible and limited damage to cardiac tissue involved in arrhythmias. In its original form, the technique involves the delivery of high energy DC discharges (fulguration) to the target area through a temporary catheter electrode. A primary drawback of fulguration, when used for ablation of AV node-His bundle, is the induction of a pacemaker-dependent state; the barotraumatic effect that results from high energy impulses constitutes the major limitation in the case of ablation of accessory pathways or arrhythmogenic areas. Recently, the efficiency of the procedure has been substantially improved by the use of low-power, high-frequency alternating current (radiofrequency), that allows to deliver graded amounts of disrupting energy to selected areas while avoiding undesirable biophysical effects to the surrounding tissue. Remarkable results, with a success rate close to 100%, are reported with radiofrequency ablation of AV node reentry tachycardia, as well as reciprocating tachycardia associated with the preexcitation syndrome, so that this technique can be considered the procedure of choice for both categories of patients. Catheter modification of AV conduction provides a therapeutic tool for treating atrial tachyarrhythmias with rapid ventricular responses. In such cases, however, the risk of AV block with the need for pacemaker implantation must be taken into account. Results of catheter ablation of ventricular tachycardia have been inconstant and generally disappointing, except for ventricular tachycardias due to reentry in the His-Purkinje system, for which a high success rate is reported. Experience with radiofrequency ablation in ventricular tachycardia is very limited, but localization of a critical segment of reentry could improve the efficiency of this technique.

Arrhythmias, Cardiac↗
PubMed1990

Transesophageal electropharmacologic test in a newborn with familial Wolff-Parkinson-White syndrome.

A newborn infant with familial Wolff-Parkinson-White (WPW) syndrome presented with a supraventricular tachycardia of 300 beats/min, refractory to digoxin and flecainide administration. Serial electropharmacologic tests were performed via the esophagus before and during oral therapy with verapamil at 40, 80, and 60 mg daily. Before treatment, tachycardia could be induced with programmed stimulation. A regimen of verapamil at 60 mg daily, which resulted in the initiation of nonsustained (less than 10 s) reciprocating tachycardia only, without clinical recurrences, was identified as suitable long-term oral therapy. The efficacy of this drug regimen in preventing episodes of tachycardia was confirmed during a 1-month follow-up period. It is concluded that transesophageal atrial pacing is a useful, noninvasive means of selecting treatment in neonates with supraventricular tachycardia, when nonconventional drugs are considered for prophylaxis.

Dose-Response Relationship, Drug↗
PubMed1990

Deceptive surgical results in three siblings with familial Wolff-Parkinson-White syndrome.

Three siblings with familial Wolff-Parkinson-White syndrome and two instances of sudden death are described. In all of them, multiple accessory pathways with a very short anterograde refractory period and rapid ventricular responses during atrial fibrillation had been documented, thus surgical ablation of the bypass tracts had been performed. Although abolition of the accessory pathway conduction had been demonstrated post-operatively, an electrophysiologic evaluation performed after 2-8 years showed resumption of conduction over the anomalous connections, with life-threatening arrhythmias during induced fast atrial rhythms. This report demonstrates that apparent success of surgery for pre-excitation syndrome, judged during the postoperative course, may be illusory in some patients, and return of accessory pathway conduction can occur later on.

Adolescent↗
PubMed1990

Electrophysiological significance of QRS alternans in narrow QRS tachycardia.

To investigate the electrophysiological significance of QRS alternans during narrow QRS tachycardia, transesophageal atrial pacing and recording was performed in 24 patients with a history of paroxysmal supraventricular tachycardia. Standard electrocardiograms showed ventricular preexcitation in 15 patients and normal QRS pattern in nine patients. The ventriculoatrial interval during tachycardia, as defined by means of transesophageal electrogram, allowed tentative diagnosis of the tachycardia mechanism. A 12-lead ECG was recorded either during spontaneous or induced tachycardia, as well as during transesophageal atrial pacing at increasing rates. Electrical alternans occurred spontaneously in eight patients (33%, group A): five with accessory pathway reentry (mean VA: 136 +/- 43 msec), and three with AV nodal reentry (mean VA: 48.3 +/- 12 msec). Tachycardia rate ranged between 170 and 230 beats/min (mean 200.7 +/- 16). In two patients, alternation of the QRS occurred only in the presence of a heart rate exceeding 180 and 190 beats/min, respectively. The amplitude of QRS remained stable during tachycardia in 16 patients (67%, group B): 14 had accessory pathway reentry (mean VA: 137.5 +/- 32 msec), and two had AV nodal reentry (mean VA: 45 +/- 7 msec). In this group, the tachycardia rate ranged from 150 to 210 beats/min (mean 175 +/- 12). Incremental transesophageal atrial pacing up to rates equal to that of tachycardia was performed in five patients from group A and in five patients from group B. Electrical alternans could not be induced in both groups with pacing at progressively increasing rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

[The diagnostic and therapeutic usefulness of adenosine triphosphate in supraventricular tachycardias].

The efficacy and safety of intravenous adenosine-5'-triphosphate (ATP) in supraventricular tachycardia (SVT) were investigated in 40 patients, aged 1 month-69 years (mean 28 years). Thirty-one had a history of paroxysmal supraventricular tachycardia (group A), 9 had chronic supraventricular tachycardia (group B). Four patients in Group A had long R-P' tachycardia. In group A, transesophageal atrial pacing was utilized for tachycardia induction. A ventriculoatrial interval (VA) during tachycardia greater than 70 ms was considered diagnostic for reentry by an AV accessory pathway (AP), while a VA less than or equal to 70 ms suggested reentry within the AV node. Serial rapid intravenous injections of graded doses of ATP were performed in both groups. In 14 patients of group A, graded doses of ATP (0.075, 0.1, 0.125, 0.15, 0.2, mg/kg) were performed in order to analyze the dose-response relationships. In group A, ATP resulted in termination of tachycardia in all patients (21 with reentry by an AP, 10 with intranodal reentry). A total of 77 tachycardia episodes were interrupted. A 100% efficacy was found with doses of greater than or equal to 0.15 mg/kg of ATP. Among patients with AP reentry, interruption in the anterograde limb of the reentry circuit occurred in 16 patients, while termination of tachycardia after retrograde block was observed in 5 patients, 4 of whom with long RP' tachycardia. In group B, ATP resulted in transient 2:1 or high degree AV block in 8 patients. Transient restoration of sinus rhythm was observed in 2 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1990

[Two to one atrioventricular block in intranodal re-entry reciprocating tachycardia. Description of 2 cases].

Atrioventricular nodal reentry tachycardia (AVNRT) is a common form of paroxysmal supraventricular tachyarrhythmia. In this tachycardia, the atrium and ventricle are not necessary links of the reentry circuit, so that the arrhythmia may persist in spite of the occurrence of 2:1 AV ratio or AV dissociation. Only a few examples of 2:1 AV block during AVNRT have been described. We report on 2 patients with a history of paroxysmal supraventricular tachycardia in whom 2:1 AV block with persistence of the arrhythmia was documented. Transesophageal electrophysiologic study was performed after pharmacologic wash-out in both patients. During definition of refractory periods, reciprocating tachycardia was initiated when a critical lengthening of the Stimulus-R interval was reached. Tachycardia showed narrow QRS complexes at a rate of 200 (patient 1) and 180 (patient 2) bpm, with the ventriculo-atrial interval (VA) of 45 and 70 ms, respectively. During tachycardia, sustained episodes of 2:1 AV block, without termination of the arrhythmia, occurred in both patients. The tachycardia could be reproducibly terminated by means of extrastimulus technique, rapid burst pacing as well as intravenous injection of adenosine-5'-triphosphate (ATP) at doses of 0.15-0.20 mg/kg. Initiation of tachycardia after a critical lengthening of the Stimulus-R interval and the effectiveness of either rapid burst pacing or ATP injection in the interruption of the arrhythmia, suggested a reentry circuit involving the AV node. The unusual finding of 2:1 AV block during reciprocating tachycardia with a retrograde time conduction (VA interval) equal to or shorter than 70 ms suggested the presence of an intranodal reentry as the substrate of the tachycardia, and excluded the presence of an accessory AV pathway.

Electrocardiography↗
PubMed1990

[Fulguration of the bundle of His. Description of 3 new cases].

With the purpose to call attention to the clinical utility of fulguration of the His bundle (a therapeutic procedure somewhat neglected in Italy) 3 new cases are presented. All patients had a long history of supraventricular tachyarrhythmias refractory to conventional treatment. Patients 1 and 2, in whom surgical correction of tetralogy of Fallot and mitral valve replacement, respectively, had been performed several years before, had chronic atrial tachycardia with congestive heart failure. Patient 3 suffered from persistent atrial flutter, in the absence of demonstrable organic heart disease. Three shocks of 320 J were necessary to induce complete AV block in patient 1 and 2. In patient 3, a single discharge (320 J) resulted in interruption of AV conduction. Twenty-four hours after the procedure, a rate-responsive ventricular pacemaker was implanted in all patients. The success of the procedure was confirmed 3 months later, during transitory pacemaker inhibition. Patients 1 and 3 exhibited atrial tachycardia and atrial flutter, respectively, but complete AV block was still present, with junctional escape rhythm at a rate of 40 and 45 b/min; in patient 2 atrial tachycardia with high degree AV block, and a mean ventricular rate of 75 b/min, were observed. Refinement of transcatheter ablative techniques is desirable. However, even in the present status, catheter ablation of the His bundle is an effective, low-risk procedure for patients with refractory supraventricular tachyarrhythmias.

Adult↗
PubMed1989

[Electrophysiologic significance of the electric alternans in supraventricular tachycardia].

To investigate the electrophysiologic significance of QRS alternans during narrow QRS tachycardia, transesophageal atrial pacing and recording was performed in 24 patients with a history of paroxysmal supraventricular tachycardia. Standard electrocardiograms (ECG) showed ventricular preexcitation in 15 patients and normal QRS pattern in 9. The ventriculo-atrial interval during tachycardia, as defined by means of transesophageal electrogram, allowed tentative diagnosis of the tachycardia mechanism. A 12-lead ECG was recorded either during spontaneous or induced tachycardia, as well as during transesophageal atrial pacing at increasing rates. Electrical alternans occurred spontaneously in 8 patients (33%, Group A): 5 with accessory pathway reentry (mean VA: 136 +/- 43 ms), 3 with intranodal reentry (mean VA: 48.3 +/- 43 ms). Tachycardia rate ranged between 170 and 230 b/min (mean 200.7 +/- 16). In 2 patients alternation of the QRS occurred only in the presence of a heart rate exceeding 180 and 190 b/min, respectively. The amplitude of QRS remained stable during tachycardia in 16 patients (67%, Group B): 14 with accessory pathway reentry (mean VA: 137.5 +/- 32 ms), 2 with intranodal reentry (mean VA: 45 +/- 7 ms). In this group, the tachycardia rate ranged from 150 to 210 b/min (mean 175 +/- 12). Incremental transesophageal atrial pacing up to rates equal to that of tachycardia was performed in 5 patients of Group A and in 8 of Group B. Electrical alternans could not be induced in both groups with pacing at progressively increasing rates. In contrast, the phenomenon was elicited in 2 patients of Group A when an abrupt pacing at the same rate that had showed the spontaneous occurrence of QRS alternans was instituted.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

[Asymptomatic pre-excitation. Identification of potential risk using transesophageal pacing].

Noninvasive assessment of the conducting capability of the accessory pathway (AP) in asymptomatic patients with a preexcitation ECG pattern is desirable, since life-threatening arrhythmias and sudden death may be the first manifestation of the Wolff-Parkinson-White (WPW) syndrome. To investigate whether in patients with preexcitation ECG pattern the absence of clinical arrhythmias excludes the potential for rapid ventricular responses, transesophageal atrial pacing (TAP) was performed in 11 subjects (9 male, 2 female), aged 5 to 43 years. The extrastimulus technique was used in order to define the refractory periods and in the attempt to induce reciprocating tachycardia. Incremental TAP up to the occurrence of block in the AP was instituted, and attempts to induce atrial fibrillation (AF) with rapid burst pacing were made. One to one atrioventricular conduction over the AP at progressively increased cycle lengths (CLs), and the shortest R-R interval between pre-excited beats during induced AF were evaluated. The following findings were considered predictors of potential life-threatening arrhythmias: 1) anterograde refractory period of the AP equal to or shorter than 250 ms; 2) one to one AP conduction at CLs shorter than 300 ms; 3) shortest R-R interval, during induced AF, less than 250 ms. Sustained reciprocating tachycardia could not be induced in all patients in spite of the use of the use of an aggressive stimulation protocol. The anterograde refractory period of the AP could not be defined in 9 patients. In the remaining 2 this parameter was longer than 250 ms. In 8 patients (72%), the shortest CL maintaining 1:1 AP conduction ranged from 220 to 280 ms (mean 253 +/- 19).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

[Transesophageal pacing in the diagnosis of accelerated atrioventricular conduction].

The term "enhanced atrioventricular nodal conduction" (EAVN) is used to indicate an electrophysiologic condition characterized by subnormal conduction delay with reduced decremental properties in the AV node, which can be responsible for rapid ventricular rates in the event of fast atrial rhythms. Although identification of such an entity usually requires definition of the AV conduction intervals, some authors have suggested that EAVN can be diagnosed, by means of atrial pacing only, when 1:1 conduction with narrow QRS complexes occurs during atrial pacing at rate higher than 200 bpm. The use of incremental transesophageal atrial pacing (TAP) as a noninvasive tool for identification of EAVN was investigated in 19 patients. Fifteen had a history of supraventricular tachyarrhythmias (11 Wolff-Parkinson-White syndrome; 2 Lown-Ganong-Levine syndrome; 1 intranodal AV reentry tachycardia; 1 sick sinus syndrome); 4 patients exhibited an electrocardiographic pattern of preexcitation without a history of tachyarrhythmias. Analysis of AV conduction at fast induced rates was hampered in 5 patients because of the easy occurrence of reciprocating tachycardia and/or atrial fibrillation during TAP, as well as because of the persistence of delta wave at cycle lengths (CL) shorter than 300 ms. Among the remaining patients, in 7 (50%, Group A), 1:1 AV conduction was present at pacing CL shorter than 300 ms. In 7 patients (50%, Group B), AV block occurred at pacing CL longer than 300 ms.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

The automatic implantable cardioverter/defibrillator: transesophageal atrial pacing discloses the potential for erroneous discharges.

We report the occurrence of erroneous discharge from an implanted automatic cardioverter/defibrillator during transesophageal atrial pacing. Transesophageal pacing was performed as part of a study protocol on the inducibility of ventricular tachycardia from the atrium in patients with ischemic heart disease. At an induced heart rate of 166 beats per minute (a value just above the cut-off rate of the device), the cardioverter/defibrillator was triggered. This observation suggests that transesophageal atrial pacing could be utilized to disclose the potential for spurious discharges in the event of fast atrial rhythms in patients with the automatic implantable cardioverter/defibrillator.

Cardiac Pacing, Artificial↗