This book will consider several clinical and interventional topics for which there is uncertainty, continued debate and/or no consensus based on current guidelines. While there are numerous guidelines in cardiology, new and on-going trials that address new drugs treatments and procedures raise many unanswered questions.  Furthermore, most practicing cardiologist taking care of the patients are likely unable to digest all of these studies or guidelines and necessarily correctly apply them to their patients. If one considers in the guidelines the frequent use of Level C (consensus), there are many areas or situations where no trial exists. Also, when applying the results of a trial to an individual patient, there can be uncertainty of how this patient should be managed based on the present body of evidence.