Cambridge Heart, Inc. RELEASE NOTES

Heartwave 1.34

This release of Heartwave software version 1.3.4 introduces the following new features:

User Interface Revisions. The Heartwave processing screen now displays two pie graphs to assist the operator in collecting at least 2.5 minutes of data between 100 and 110 bpm and at least 1.5 minutes of data between 110 and 120 bpm.

The first pie graph measures the amount of time the patient’s heart rate remains between 100 and 110 bpm. For accurate alternans processing, the HR should remain in the highlighted band between 100 and 110 bpm for at least 2½ minutes. At the 2½-minute mark, the timer fills in completely.

A line inside the pie graph indicates the point at which it becomes 60% filled. If the heart rate rises above 110 bpm before the pie is at least 60% filled, the test is likely to be indeterminate due to a too-rapid rise in heart rate.

Second pie graph

The second pie graph measures the amount of time the patient’s heart rate remains between 110 and 120 bpm. For accurate alternans processing, the HR should remain in the highlighted band between 110 and 120 bpm for at least 1½ minutes. At the 1½-minute mark, the timer fills in completely.

A line inside the graph indicates the point at which it becomes 60% filled. if the heart rate is not sustained between 110 and 120 for a long enough period to fill at least 60% of the pie, the test is likely to be indeterminate due to insufficient heart rate.

When the second pie graph is 100% filled, a single beep sounds. Tthe “Proceed to recovery” message appears, prompting the operator to end exercise and allow the heart rate to recover to below 90 bpm (or the resting level, if higher) before printing reports.

Signal Processing Enhancements. Also to reduce the number of indeterminate tests, the threshold for bad beat artifact used by the classifier has been increased from 10% to 15%. This change has been shown to cause no loss in negative or positive predictive value. In addition, the prematurity thresholds used in bad beat replacement and Rbb calculation have been modified, from 0.90 to 0.85 for the current beat and from 0.90 to TQ 132ms for the following beat. Heartwave software version 1.3.4 introduces a further enhancement in signal processing methods. The enhancement allows for improved capability in detecting microvolt level T-wave alternans in the presence of a larger number of bad beats. As a result, the threshold for bad-beat artifact used by the classifier has been increased from 10% to 15%.