| 摘要 |
An implantable cardioverter/defibrillator and method for its use. A sensing electrode provides an ECG signal to the defibrillator, this signal is amplified and evaluated for the presence of a tachyarrhythmia. The phase of the ECG signal is sensed during a detected fibrillation or tachycardia and this determines the phase of the stimulating output signals. The ECG may be continuously sensed during the application of the defibrillating output and each output is held constant until a threshold crossing of the ECG is detected, whereupon the defibrillating output is changed. The system may also be configured to generate outputs in response to the ECG signal exceeding one or more thresholds. The defibrillating output is generated as a constant current output. The ECG amplifier compensates for a resultant offset voltage with an autozero loop. The specific lead configuration and the patient's condition are considered in programming the amplitude and polarity of the defibrillation output. In an alternative embodiment, the phase of the ECG signal is detected and an output of predetermined duration is delivered. In this configuration, it is not necessary to sense the ECG during the output. The system may also be used in a preconditioning mode wherein the phase related output is followed by a conventional high voltage monophasic or biphasic defibrillation waveform. The ECG is monitored for return to normal rhythm and the output stimulation is discontinued when normal rhythm is restored.
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