Catálogo de publicaciones - libros

Resetting responses and response to entrainment have confirmed the reentrant nature of flutter and established the presence of a fully excitable gap in the majority of patients. During atrial flutter, the use of 3D electroanatomic mapping studies and the entrainment pacing technique have aided in defining the mechanism of the arrhythmia with the activation sequence, providing information regarding the timing of intra-atrial events with respect to the surface electrocardiogram, especially for the non-CTI-dependent form and for left flutter.

Further study will be needed, however, to definite the precise boundaries of flutter and to better identify correlations between the location of the different electrophysiologic types of reentrant circuits and their electrocardiographic characteristics.

The literature on ablation for AF has many of the features of clinical research in the era preceding evidence-based medicine and randomised trials. Many studies emanate from single centres, involve low patient numbers, and fail to provide adequate statistical analysis, including intention to treat analysis and evaluation of statistical power. As was the case with Maze operations, new procedures are continually proposed without completing satisfactory evaluations of previously proposed procedures. Very worrisome is that most studies have not involved neutral committees for the recording and supervision of severe complications.

The belief that AF ablation now represents a standard or, indeed, first-line treatment is excessively optimistic and may reflect occupational and economic factors encouraging mechanistic invasive procedures.

TEE is a useful tool to investigate patients undergoing ablation therapy of atrial fibrillation. The technique provides important information about the presence of thrombus and SEC in the left atrium and LAa, and about minor IAS abnormalities, which seem to occur more frequently than in the normal population. Such information is necessary for planning the approach to the PV by catheters that must cross the septum and the atrial cavity.

After ablation, TEE can be used to monitor possible minor complications, such as a residual IAS shunt or pericardial effusion. It also allows the detection of PV stenosis, a rare but dreaded complication of PVAI. A control TEE examination 3 months after the ablation procedure is probably adequate for this purpose.

Atrial and dual defibrillators held great promise when they were introduced in the 1990s.

The devices are effective and safe in selected patients. Tolerability and acceptance by patients is good in the short term but only moderate in the longer term. The complication rate is relatively low. However, advances in ablation techniques for the treatment of atrial fibrillation have limited and will continue to limit the use of implantable atrial defibrillators. In combination with ICDs they may find a continued role in a patient group that should be further defined.

Both triggers and an atrial electrophysiologic substrate contribute to the development of AF episodes. In the absence of structural heart disease, AF itself promotes a substrate due to electrical remodeling by shortening of refractoriness. However, before this remodeling susceptibility to AF is due to an initiating substrate. This substrate facilitates reentrant mechanisms and appeared to be due to enhanced spatial dispersion of refractoriness. The initiating substrate is associated with a minor form of Cx40 polymorphism in selected patients. Further studies are needed to confirm this relationship in other patient categories and to assess causation.

Available evidence supports the hypothesis that CRT results in favourable structural and electrical remodeling. Whether this effect would obviate the need for back-up defibrillation capability in CRT devices is unclear and should be the focus of further studies.

The progression of atrial fibrillation may be explained by the above-described effects of atrial remodelling. Maintaining sinus rhythms in atrial fibrillation by whatever means may slow the progression of remodelling and give patients benefit until safer antiarrhythmic drugs and ablation procedures are developed.

Atrial flutter may occur as a complication of PCI, but most of the time the Patients’ characteristics play important roles in the occurrence of this type of arrhythmia. For instance, ongoing acute MI can be the real reason for AF. Generally, AF tends to revert spontaneously, but when necessary treatment must be given promptly. If the patient is compromised by ventricular rate or by the loss of atrial contribution to cardiac output, synchronised DC cardioversion should be performed without delay. Intravenous beta-blockade can be effective for acute rate control. Calcium-channel blockers can be administered to promptly control ventricular rate. Digoxin, amiodarone and dofetilide are the drugs of choice for treating patients with acute MI with heart failure.

Atrial flutter may occur as a complication of PCI, but most of the time the Patients’ characteristics play important roles in the occurrence of this type of arrhythmia. For instance, ongoing acute MI can be the real reason for AF. Generally, AF tends to revert spontaneously, but when necessary treatment must be given promptly. If the patient is compromised by ventricular rate or by the loss of atrial contribution to cardiac output, synchronised DC cardioversion should be performed without delay. Intravenous beta-blockade can be effective for acute rate control. Calcium-channel blockers can be administered to promptly control ventricular rate. Digoxin, amiodarone and dofetilide are the drugs of choice for treating patients with acute MI with heart failure.