Methods and apparatus for detecting heart failure event using impedance vector switching

摘要

Devices and methods for detecting physiological target event such as events indicative of heart failure (HF) decompensation status are described. An ambulatory medical device (AMD) can detect device site maturation such as in a device encapsulation pocket, and classify the maturation status into one of two or more device site maturation states. The AMD can include an electrical impedance analyzer circuit that can measure a first maturation-insensitive impedance vector and a second maturation-sensitive impedance vector. At least one impedance vector can be selected or a composite impedance vector can be generated in accordance with the classified device site maturation state. The AMD can generate an impedance indicator using the selected or composite impedance vector, and detect a target physiologic event indicative of worsening of HF using the impedance indicator.

主权项

1. A system, comprising:
an ambulatory medical device (AMD) including:
an electrical impedance analyzer circuit, including:an impedance sensing circuit configured to be capable of measuring from a patient first and second impedance vectors, the first impedance vector having a lower predicted sensitivity to device site maturation than the second impedance vector;an impedance vector selector circuit configured to select the first impedance vector during device site maturation, and to select the second impedance vector once device site maturation has occurred; andan impedance indicator generator circuit configured to generate an impedance indicator indicative of a target physiologic event using the selected first impedance vector during the device site maturation, and using the selected second impedance vector after the device site maturation has occurred; and a physiologic event detector circuit coupled to the electrical impedance analyzer circuit, the physiologic event detector configured to predict or detect the target physiologic event using the impedance indicator.