Apparatus and methods for automatic adjustment of av interval to ensure delivery of cardiac resynchronization therapy

Abstract

The disclosure provides methods and apparatus of left ventricular pacing including automated adjustment of a atrio-ventricular (AV) pacing delay interval and intrinsic AV nodal conduction testing. It includes—upon expiration or reset of a programmable AV Evaluation Interval (AVEI)—performing the following: temporarily increasing a paced AV interval and a sensed AV interval and testing for adequate AV conduction and measuring an intrinsic atrio-ventricular (PR) interval for a right ventricular (RV) chamber. Thus, in the event that the AV conduction test reveals a physiologically acceptable intrinsic PR interval then storing the physiologically acceptable PR interval in a memory structure (e.g., a median P-R from one or more cardiac cycles). In the event that the AV conduction test reveals an AV conduction block condition or if unacceptably long PR intervals are revealed then a pacing mode-switch to a bi-ventricular (Bi-V) pacing mode occurs and the magnitude of the AVEI is increased.

1 . A method of left ventricular pacing including automated adjustment of a atrio-ventricular (AV) pacing delay interval and intrinsic AV nodal conduction testing comprising—upon expiration or reset of a programmable AV Evaluation Interval (AVEI)—performing the following steps: 
 temporarily increasing a paced AV (PAV) interval and a sensed AV (SAV) interval and a. testing for adequate AV conduction and b. measuring a median intrinsic atrio-ventricular (PR) interval for a first-to-depolarize ventricular chamber for at least three consecutive cardiac cycles, storing:    in the event that the AV conduction test reveals a physiologically acceptable intrinsic PR interval for said ventricular chamber then storing the physiologically acceptable median PR interval in a memory structure;    subtracting approximately 30 milliseconds from the median PR interval to define a pre-excitation interval (PEI);    in the event that the AV conduction test reveals unacceptably long PR intervals then: 1. performing a pacing mode-switch to a bi-ventricular (Bi-V) pacing mode and 2. increasing the magnitude of the AVEI; and    delivering a pacing stimulus to the last to depolarize ventricle approximately at the expiration of the PEI.    
   
   
       2 . A method according to  claim 1 , further comprising calculating an FAV delay interval for paced atrial events (F-PAV interval) and for sensed atrial events (F-SAV interval) and storing at least one of the F-PAV interval and the F-SAV interval in a first-in-first-out memory buffer.  
   
   
       3 . A method according to  claim 1 , further comprising: 
 delivering a single pacing stimulus to a left ventricular (LV) chamber at the expiration of the FAV delay interval.    
   
   
       4 . A method according to  claim 1 , wherein the AVEI comprises one of a temporal unit and a number of cardiac cycles.  
   
   
       5 . A method according to  claim 1 , wherein the AVEI expires or is adjusted based upon one of: a detected level of activity of a patient, a heart rate of the patient, a rate of change of the heart rate of the patient.  
   
   
       6 . A method according to  claim 2 , wherein the step of calculating an FAV delay interval for paced atrial events is based on the SAV interval is performed according to the mathematical relationship:  
         A   sp   CO =( A   p - RV   s )−( A   s - RV   s )  
     wherein A sp CO stands for an Atrial Sense/Atrial Pace Conduction Offset value.  
   
   
       7 . A method according to  claim 6 , further comprising periodically updating the A sp CO value.  
   
   
       8 . A method according to  claim 1 , further comprising: 
 immediately halting the performance of the claimed method based on satisfaction of one of a preselected criteria and predetermined condition; and    performing a pacing mode-switch to a bi-ventricular (Bi-V) pacing therapy.    
   
   
       9 . A method according to  claim 8 , wherein one of the preselected criteria and the predetermined condition comprises: a detection of a tachycardia episode, an occurrence of the tachycardia episode, a probability of the tachycardia episode, a detection of an arrhythmia, an AV conduction block condition, a prolonged AV conduction condition.  
   
   
       10 . A method according to  claim 9 , wherein the tachycardia episode comprises one of a ventricular tachycardia episode and a ventricular fibrillation episode.  
   
   
       11 . A method according to  claim 8 , wherein subsequent to one of the preselected criteria and the predetermined condition being satisfied waiting for a nominal interval and then performing at least one of the following: 
 performing the method of  claim 1  without utilizing any prior temporal values;    delay at least one AVEI and attempt to perform the method of  claim 1;     in the event that a programmable period of time has expired, then switching to Bi-V pacing therapy; and    adjusting a PVARP blanking interval for a programmable period of time.    
   
   
       12 . A method according to  claim 1 , further comprising: 
 wherein one of the rate of change and the magnitude of change from a prior FAV delay interval to a new FAV delay interval are constrained to a programmable increment.    
   
   
       13 . A method according to  claim 12 , wherein the programmable increment comprises between about five milliseconds and about thirty milliseconds.  
   
   
       14 . A method according to  claim 1 , further comprising: delivering a ventricular pacing pulse following a predetermined period of time during the AV conduction test.  
   
   
       15 . A method according to  claim 14 , wherein the pacing pulse is delivered at approximately 350 ms following detection of an atrial event.