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Ann Thorac Surg 1995;59:275-276
© 1995 The Society of Thoracic Surgeons
Division of Cardiothoracic Surgery, East Carolina University School of Medicine, Greenville, North Carolina
National surveys are among the most difficult studies to plan, complete, interpret, and generate the appropriate fanfare for. This is especially true when attempting to track a diffuse and ever-changing topic such as myocardial protection. Opinions of surgeons as to optimal methods of intraoperative cardioprotection remain varied, empiric, and near dogmatic. For these and other reasons statistically sound data often are difficult to derive from surveys. In this edition of The Annals, Robinson and associates [1] have provided a well-conceived, comprehensive survey of current myocardial protective strategies from surgeons treating acquired cardiac disease. Moreover, their work has tracked the evolution of this technology through comparisons with earlier surveys.
Survey questionnaires take a great deal of time and effort to develop to obtain a maximal response. It is difficult to determine what factors influence response rates of surgeons to surveys. In the era of increasing paper work, busy surgeons seem even less inclined to fill out elective questionnaires. Response rates to seven general myocardial protection surveys since 1977 have
varied from 24% to 64% [2–8]. A lower response rate (32%) to the present survey perhaps resulted from the lengthy questionnaire (86 questions). However, the two-mailing effort of Robinson and associates maximized potential responses to this survey. At the same time, Izzat and colleagues [8] received a 87% response rate from 120 English consultant surgeons. Thus, the questionnaire becomes the ``lure'' and the surveyor somewhat of a ``fly fisherman.'' It is important to construct questionnaires in an attractive, short format for the queried surgeon to ``strike.'' At the same time there must be adequate data obtained to cover the demographic and technical aspects of the subject.
Before the present survey, Miller and associates [2–4] provided excellent comparative surveys in 1976, 1980, and 1982. Each study provided a vignette of myocardial protection and perfusion strategies in an earlier era. Subsequent surveys provided selective updates but were less comprehensive than those of Miller and associates. However, from these we were able to track the adoption, evolution, and sometimes rejection of many seemingly promising techniques. A graphic reflection of the importance of a clinical survey can come from examining a specific technique. In 1986 Beggerly and associates [5] reported that fewer than 1% of surgeons had even attempted to use retrograde coronary sinus cardioplegia. Four years later 72% of respondents to a survey by Chitwood [7] had used retrograde cardioplegia. As shown in Robinson and associates' study [1], by 1992, 64% of cardiac surgeons had adopted this technique for routine use. Thus, serial surveys served to emphasize the developing consensus that retrograde cardioplegia is used much more frequently as a safe, effective route for cardioplegia.
As pointed out by Robinson and associates, surveys of this type have inherent weaknesses. The goal of a clinical survey is to provide contemporaneous practice data. However, this becomes impossible because of necessity of data collection and analysis, manuscript preparation, editorial review, and publication backlogs. In addition, busy practicing surgeons usually rely on memory to complete the form. Rarely do surgeons refer to a local database to confirm the impression expressed on the questionnaire. In the future surgeons may use both local and national databases to catalog and collate data relating to myocardial protection. Moreover, integration of this information with mortality and morbidity data will give us a better idea of the efficacy of protective methods. Despite these hopes, the level of detail chronicled by Robinson and associates' survey is not likely on a continuous basis, even with the most sophisticated professional society database. Finally, in any large survey the queried sample may not be representative. This survey encompasses 32% of all cardiac cases in the United States for the period studied. Thus, it is unlikely that a sampling error could occur. However, responding surgeons mentally refer to a standard technique; therefore, omission of applications to more complex cases, such as reoperations and multiple operations, could skew the data.
Despite these inefficiencies, salient survey information gives the reader a notion of what is happening in myocardial protection. As 78% of respondents were pleased with their method of protection, readers may be more interested in general themes that emerged from the survey. Several of these merit comments. Regional variation was reflected in the type of cardioplegia as well as route and temperature of administration. The reasons for this are obscure but probably relate to different methodologies taught in regional training programs. Blood cardioplegia was used more often by western surgeons, and this may have reflected a specific influence by those who were instrumental in developing these methods.
Although warm blood cardioplegia had received maximal notoriety, only 10% of surgeons included in this survey used it routinely. Compared with the level of excitement generated by zealous proponents of warm cardioplegia, most readers would have guessed greater application even by 1992. A survey completed today may show increasing use of warm cardioplegia; however, recent randomized clinical studies may have mollified selection as well. Thus, isolated surveys may never be very effective for assessing rapid fluxes in technology. Finally, it is noteworthy that more senior surgeons were more flexible in adopting new techniques. Moreover, surgeons with less clinical volume tended to adopt a more maximal protective approach but were less satisfied with the method they were using currently. One would have considered the young surgeon to select new methodologies more easily; however, many still could be influenced by their training. It would be interesting to determine how often surgeons in practice less than 5 years use the same myocardial protective strategy as their residency mentors.
As stated by Robinson and associates, ``The results of this survey . . . [provide] the interested reader a means of self-assessment for comparison with his or her peers.'' Clearly, Alexander Pope's statement, ``Be not . . . the last to lay the old aside,'' has relevance with relation to surveys. The world of intraoperative myocardial protection has consumed much of our literature for the last 20 years, yet no absolute consensus exists as to the ``best method.'' Surveys have a place to help determine what is successful for the practicing surgeon. Although many surgeons are pioneers, most live by consensus, and the selection of a proven technique remains important. We all still look for the Holy Grail to emerge from the luminaries in the field but may learn just as much from daily clinical application. Surveys may provide the closest guideline for the younger surgeon still struggling to select a method that protects his or her patients best. Although it is difficult to derive the perfect myocardial protection survey, Dr Robinson and his co-workers have done a yeoman's job in collecting and assimilating these important data. Despite drawbacks, surveys have provided us with a ragged continuum relating the evolution of current myocardial protective and general perfusion techniques. Clearly, it is important for all of us to participate with interest in these types of well-organized surveys. Moreover, it is most important that thoracic surgeons remain in charge of determining the efficacy of our operative technology.
Footnotes
Address reprint requests to Dr Chitwood, Division of Cardiothoracic Surgery, East Carolina University, 200 Stantonsburg Rd, Greenville, NC 27858.
References
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