Protection of the Heart With Doxycycline During Coronary Artery Bypass Grafting

• Doxycycline, a tetracycline antibiotic that also possesses secondary inhibitory effects on matrix metalloproteinases (MMPs), will attenuate myocardial and systemic activation of MMPs if administered to patients prior to the onset of CPB. [ Time Frame: 2 days prior to surgery until 3 days post operative ] [ Designated as safety issue: No ]
  

• Attenuating the activation of MMPs will reduce cleavage of contractile protein regulatory elements such as troponin I (TnI) and myosin light chain 1 (MLC-1), which will improve cardiac functional recovery after CPB. [ Time Frame: 2 days prior to surgery until 3 days post operative ] [ Designated as safety issue: No ]
  

Drug: Periostat
In addition to standard care, patients will receive oral administration of 20 mg of doxycycline or placebo twice a day at least 2 days prior to surgery, on the day of surgery, and on postoperative days 1, 2, and 3.

This proposal is for a randomized, placebo-controlled, double-blinded study of the use of doxycycline in patients requiring CABG surgery. Patients will be randomized 1:1 to receive either doxycycline or placebo.

This study will be conducted in a blinded manner. The pharmacy will randomize patients and will have the randomization code. The code will only be broken in the case of an emergency and the event will be fully documented.

In addition to standard care, patients will receive oral administration of 20 mg of doxycycline or placebo twice a day at least 2 days prior to surgery, on the day of surgery, and on postoperative days 1, 2, and 3.

Myocardial atrial biopsies will be taken at 2 time points during the CABG procedure: during cannulation of the right atrium and 10 minutes after cross-clamp release. Tissue will be analyzed for MMP-2 and -9 activity and TnI and MLC-1 levels.

A Swan-Ganz-Catheter will be placed in the pulmonary artery over 24 hours to measure hemodynamics (LVSWI).

A coronary sinus catheter will be placed under echocardiographic guidance prior to initiation of CPB (will be removed 20 minutes after cross-clamp release).

Patients will have an additional ECG on post-operative days 1 and 3.

Additional blood will be drawn to determine doxycycline plasma levels, MMP-2 and -9 activity, total gelatinolytic activity, and levels of troponin I and T products at the following time points: pre-induction, prior to initiation of CPB, 10 and 20 minutes following the release of the aortic cross clamp (arterial and venous) and 3, 6, 24 and 72 hours post aortic cross clamp removal (venous). Each of the above samples will require 6 mL of blood for a study total of 72 mL. At the time of each blood draw we will measure and record the hematocrit value.