Thyroid storm and arrhythmic storm: a potentially fatal combination.

Thyroid storm is a rare clinical emergency with a mortality rate between 20% and 30%. Cardiac arrhythmias associated with thyrotoxicosis are usually supraventricular. Ventricular arrhythmias are rarely associated with this entity and tend to occur in patients with intrinsic cardiac disease. We present a 35-year-old woman with Graves disease and a thyroid storm manifested with multiple malignant dysrhythmic episodes, without underlying cardiac disease. The mechanism for ventricular arrhythmia is not clear but seems to be due to the increased myocardial excitability directly caused by the thyroid hormones. The presence of myocarditis lesions may constitute an arrhythmogenic substratum and contribute further to this manifestation. This case emphasizes the importance of cardiac monitoring in patients with thyroid storm.

[Circumferential pulmonary vein isolation with the cryoballoon technique]. / Isolamento circunferencial das veias pulmonares com a técnica do criobalão.

We present a clinical case on cryoballoon ablation of paroxysmal atrial fibrillation. This is a report of the first case performed at our center using this new technology.

Atrial fibrillation ablation using simultaneous multielectrode application of radiofrequeney energy.

Despite technological advances in equipment for ablation of atrial fibrillation (AF), conventional pulmonary vein (PV) isolation with point-by-point radiofrequency application encircling the PV ostia remains a complex procedure requiring a high degree of operator skill and experience. Novel multielectrode catheters have been developed that deliver duty-cycled bipolar and unipolar radiofrequency energy, designed for PV electrical isolation and for ablation of complex fractionated electrograms in the left atrium. Initial studies suggest good results, reducing procedure time and with safety and efficacy equivalent to the conventional method. We describe the first four cases of AF ablation in our center using this method, with acute success in two patients: one with paroxysmal AF and the other with chronic AF.

Ventricular tachycardia ablation in patients with coronary heart disease: beyond the reentry circuit.

INTRODUCTION: Patients with coronary heart disease and left ventricular dysfunction are at increased risk for the development of ventricular tachycardia (VT) related to areas of myocardial fibrosis. Although the mechanism and the circuit of this arrhythmia are well understood, little is known about the triggers that precipitate VT episodes. Purkinje fiber potentials may be responsible for idiopathic VT, and recent studies have related them to polymorphic VT and ventricular fibrillation. METHODS: Between January 2002 and December 2003, we performed ablation in 10 patients with coronary heart disease, left ventricular systolic dysfunction and VT refractory to pharmacological therapy. All patients had implantable cardioverter-defibrillators. Electroanatomical activation and voltage mapping (CARTO) and electrophysiological criteria (premature activation during VT, pace mapping, and presence of diastolic potentials) were used to define scar regions, slow conduction areas and the reentry circuit isthmuses. RESULTS: Spike potentials were recorded in the scars of three patients. These potentials were almost fused with the ventricular electrogram during sinus rhythm, and were more premature during VT, probably reflecting local activation of Purkinje fibers. During ablation, we were able to dissociate the spike from the ventricular electrogram, thus terminating the VT. In the cases with conduction recovery, ventricular; ectopic beats recurred, preceded by a spike and degenerating into short runs of VT. The ablation strategy was not modified since persistence of the VT required the isthmus. CONCLUSION: The results suggest that residual Purkinje fibers may be present in scar regions and that the activity of these fibers may trigger VT in pre-established circuits.