W. H. Wilson Tang - Cardiorenal Syndrome in Heart Failure

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Heart failure continues to be a major medical problem across the globe. In the United States (US), it is the most common reason for patients to be hospitalized. Hospital cases of heart failure with preserved ejection fraction (HFpEF) are increasing in the US, while hospitalization for heart failure with a reduced ejection fraction (HFrEF) may be decreasing. Both conditions often present with fluid overload, pulmonary congestion, edema, and some renal function impairment. Most physicians know that aggressive diuretic therapy or other means of reducing excessive circulating volume can at times lead to worsening renal function and even acute kidney injury. When this occurs in the setting of acute decompensated heart failure, outcomes can be poor, and management can be challenging.

This important new book brings together the clinician-scientists that have been actively studying the cardio-renal syndrome at various universities around the world. The authors know each other well and have been at the front lines in various laboratories trying to better understand what is really happening and how it can be best managed. It is most appropriate that they have come together to put forth their thinking into this book in 18 extraordinary chapters.

I know most of these investigators. Some, such as John Burnett, I have known for longer than John and I would care to divulge. In the early days of heart failure research, John's lab group in Rochester (Mayo Clinic) and ours at the University of Minnesota used to meet regularly to share data to better understand the important role of the kidney in heart failure. The effervescence of the lab meetings was stunning! We learned a great deal from each other and uncovered the things we did not know!

When I moved to the Cleveland Clinic, I worked closely with W. H. Wilson Tang and Wilfried Mullens. It was a time of extraordinary focus on the kidney in heart failure, which Wilson and Wilfried have continued, now on both sides of the Atlantic. Other prominent investigators have participated in elegant studies on the kidney in patients with heart failure, and many of them have contributed their insights in this book. The cast is really quite remarkable. Most are still very actively investigating this complex interplay between the kidney and the failing heart.

I am honored that I was asked to write this short forward for this important new book. These authors are the people that have done the work, and we need to listen to them. There are other investigators, not represented here, who of course have also made major contributions to the field and we are most grateful for their work over the years. Credit goes to Drs. Tang, Verbrugge, and Mullens for updating the field and for putting this book together. It is outstanding!

The topic of cardio-renal syndrome has been reviewed extensively in the literature especially the past few decades. There is general agreement that adverse and dynamic interactions between the kidneys and circulatory compartments promote increased circulating volume, exacerbate heart failure symptoms, and accelerate subsequent disease progression, while the contribution of noncardiac factors is also under-recognized. Nevertheless, this complex and diversified condition cannot be confined to a one-fits-all approach when patients presents with a wide range of manifestations. Often, thorough insight and understanding of cardiac and renal pathophysiology in heart failure and kidney disease is key for making the right therapeutic decisions. Many classic theses of congestive failure and edema have been developed since the 1940s, among them were writings from legends like Issac Starr and Eugene Stead to address these age-old bedside dilemmas [1, 2]. These elegant masterpieces often read like fireside chats and reminded us the importance of logical reasoning and pathophysiologic deductions that was based on astute bedside observations and presentations of individual patients or case series. As clinicians, there is a need to look back at the often-forgotten wisdom from the past and to better integrate them with new tools and insights now available in the pursuit of precision medicine.

Like such master clinicians, this book seeks experts in various topics of cardio-renal syndrome to incorporate pathophysiologic insights in describing their approaches to various clinical scenarios that clinicians often encounter in managing heart failure. As editors, we are honored to bring together a group of international experts in which every senior author has made a huge contribution to advance the field of cardio-renal medicine while bringing together many of the learnings we have collectively made over the past decades. By design, we commenced this book with a historical perspective on the evolving evidence and concepts regarding cardio-renal syndrome, combined with perspectives on the contemporary understanding of cardio-renal interactions in the setting of heart failure. These introduction chapters set the stage for some in-depth discussions of traditional and novel pathophysiological insights on neurohormonal and autonomic mechanisms as well as clinical pharmacology perspectives all forming the backbone for later case-based chapters. It has been the aim to offer a thorough mechanistic understanding of problems that are frequently encountered in clinical practice and directly apply this knowledge through practical recommendations. Each starts with a realistic case vignette of a patient with cardio-renal syndrome. Building from the cases, key questions are posed that are relevant to the clinical management. This is followed by a brief discussion of the available evidence for diagnosis and/or treatment, citing key insights over the years from research groups across the globe. Finally, a treatment strategy is proposed with a link back to the case vignette and the pathophysiology that is discussed in the earlier chapters.