Log query For Heart beat Alerts with Exemption

Hi All,

I am using the below log query for Heart beat alerts. In this query i need to include the line which ignores the servers which are not needed for Heartbeat alerts. Basically if the TAG is updated with comments that this particular server is in maintenance or auto shutdown schedule that TAG should be noted and query should not execute for that particular servers. 

Heartbeat

| where Computer contains "VM"

| summarize LastHeartbeat=max(TimeGenerated) by Computer

| where LastHeartbeat < ago(15m)

Thanks,

Vignesh