Expiring patents for best-selling cardiovascular drugs, including Bristol-Myers Squibb and Sanofi's anti-clotting drug Plavix and Pfizer's cholesterol-lowering treatment Lipitor, have left drugmakers scrambling for next-generation replacements. The patent losses could drag down sales of cardiovascular drugs to $60 billion by 2017 from $83 billion last year, according to analysts' forecasts.