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Atrial Pacing
595 Correspondence
ventricle-to screen out the R-waves in the atrium. This is particularly important in the unipolar mode but may not be so important in the bipolar mode; far-field signals, such as those of the QRS complex, appear much smaller with a bipolar lead because of the smaller antenna area. Finally, the pulse generator used to pace the atrium should at least have the option of triggered mode programmability. This feature allows for external overdrive in the postoperative period to check for the development of possible atrioventricular conduction disturbances after insertion of an atrial pacing system. Tripolar conversion to permit the use of the bipolar bifocal atrioventricular sequential system is certainly valid, and has been used successfully by others.
Nicholas P . D . S m y t h , M . D . Physicians Office Bldg, Suite 220 106 Irving S t , N W Washington, DC 20010
Reply To the Editor: Dr. Smyth’s comments on our paper are greatly appreciated. We agree with him that the use of a nonprogrammable unipolar ventricular pulse generator in the atrial position should be limited to patients with specific clinical characteristics. It must be emphasized, however, that with the increasing use of multiprogrammable ventricular pulse generators,
conversion from ventricular to atrial pacing will be made possible by increasing the refractory period and changing the sensitivity to a greater value.
Diego A.Bognolo, M . D . 13550 N . 31st S t , Suite 220 Tampa, FL 33612
Intrauterine Surgery To the Editor: The laudable and fascinating paper entitled “Intrauterine Cardiothoracic Surgery: The Fetal Lamb Model” by Turley and colleagues (Ann Thorac Surg 34:422, 1982) provides further proof that intrauterine surgery is a reality. It also raises an ethical dilemma: How do we physicians reconcile the contradiction between using life-preserving technology for some unborn children, while permitting the life-taking practice of abortion for others? The only consistent approach demands the humane application of our healing art to all our patients, born and unborn.
William V . Dolan, O . F . M . , M . D . (Order of Friars Minor)
Convento Siio Francisco Av Siio Sebastiiio 517 Caixa Postal 191 tarCm -Para Brazil
68.1 00-San
ventricle-to screen out the R-waves in the atrium. This is particularly important in the unipolar mode but may not be so important in the bipolar mode; far-field signals, such as those of the QRS complex, appear much smaller with a bipolar lead because of the smaller antenna area. Finally, the pulse generator used to pace the atrium should at least have the option of triggered mode programmability. This feature allows for external overdrive in the postoperative period to check for the development of possible atrioventricular conduction disturbances after insertion of an atrial pacing system. Tripolar conversion to permit the use of the bipolar bifocal atrioventricular sequential system is certainly valid, and has been used successfully by others.
Nicholas P . D . S m y t h , M . D . Physicians Office Bldg, Suite 220 106 Irving S t , N W Washington, DC 20010
Reply To the Editor: Dr. Smyth’s comments on our paper are greatly appreciated. We agree with him that the use of a nonprogrammable unipolar ventricular pulse generator in the atrial position should be limited to patients with specific clinical characteristics. It must be emphasized, however, that with the increasing use of multiprogrammable ventricular pulse generators,
conversion from ventricular to atrial pacing will be made possible by increasing the refractory period and changing the sensitivity to a greater value.
Diego A.Bognolo, M . D . 13550 N . 31st S t , Suite 220 Tampa, FL 33612
Intrauterine Surgery To the Editor: The laudable and fascinating paper entitled “Intrauterine Cardiothoracic Surgery: The Fetal Lamb Model” by Turley and colleagues (Ann Thorac Surg 34:422, 1982) provides further proof that intrauterine surgery is a reality. It also raises an ethical dilemma: How do we physicians reconcile the contradiction between using life-preserving technology for some unborn children, while permitting the life-taking practice of abortion for others? The only consistent approach demands the humane application of our healing art to all our patients, born and unborn.
William V . Dolan, O . F . M . , M . D . (Order of Friars Minor)
Convento Siio Francisco Av Siio Sebastiiio 517 Caixa Postal 191 tarCm -Para Brazil
68.1 00-San