Case Presentation:
A 77 year old Caucasian male presented for further care of ischemic cardiomyopathy and ambulatory class IV heart failure symptoms. His past medical history included pacemaker placement for complete heat block, triple vessel bypass surgery for coronary artery disease and hypertension. An attempt was made to upgrade the pacemaker to Cardiac Resynchronization Therapy‐defibrillator (CRT‐D) for treatment of his low LVEF (less than 35%), heart failure symptoms and wide QRS complexes. In that operation, the left ventricular lead could not be placed through the coronary sinus due to reported significant intravascular fibrosis. He was then referred to our center for second opinion. On examination, lungs were clear, heart examination was remarkable for a soft S3 and extremities for mild pedal edema. EKG showed a right ventricular pacing rhythm.
After discussing the options, the patient requested another attempt at placing a transvenous LV lead. A new LV lead was successfully implanted through coronary sinus into a lateral branch vein and the CRT system was completed. He improved significantly following this CRT upgrade into a NYHA class III heart failure status. However he continued to have some limitation due to residual exertional dyspnea. CRT reprogramming using gas exchange was undertaken, using the Shape HF cardiopulmonary exercise system (Minneapolis, MN), to address his remaining dyspnea. Based on the findings, ventriculo‐ventricular (V‐V) timing was optimized and poor chronotropic response was addressed by adjusting the device’s rate response thresholds. He clinically improved to and remained at a NYHA class II status at one year follow up evaluation. Interrogation and testing of his CRT‐D at this visit showed appropriate biventricular pacing and stable thresholds.
Discussion:
In multicenter trials, 40% of patients receiving CRT do not have significant clinical improvement, and are considered non‐responders. It is not clear if they simply do not show benefit with CRT or if it is due to inadequate programming. The optimization of CRT programming involves a variety of techniques. Here we utilized gas exchange for CRT optimization. The important links between respiratory function and cardiac disease severity and in combination with heart rate response to exercise provide a basis for functional optimization of CRT. An algorithm is designed from various studies to assess the impact of various A‐V and V‐V intervals during submaximal exercise. SHAPE system has reliably identified the timing cycles that correlate best with the ventilator parameters. Accordingly A‐V and V‐V timing can be adjusted dynamically, using gas exchange during exercise, and frequent optimization is associated with improved long‐term clinical response in CRT‐pacemaker patients.
Conclusions:
CRT optimization using gas exchange is a newer technique and may help the significant number of non‐responders when other issues such as adequate LV lead location have been accomplished.