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Hazard Function Technology
Contact us at: email@example.com
Some of the most relevant outcomes of medical procedures, or of the life-history of machines, are time-related events. The "raw data" for such events is the time interval between some defined "time zero" (t=0) and the occurrence of the event. The distribution of a collection of these time intervals could be viewed as a cumulative distribution table or graph, although commonly the compliment of the cumulative distribution is displayed as a so-called survivorship function. Another way to visualize the intervals would be as a histogram or probability density function; however, because the fundamental questions about these intervals relates to some biologic or natural phenomenon across time, the more natural domain for study is as the rate of occurrence.
The rate of occurrence of a time-related event is known as the hazard function. John Graunt brought this word from dicing into the arena of time-related events during the 17th century. It is sometimes called the "force of mortality." In financial circles, it is the inverse of Mills ratio.
Actually, all one is dealing with is the distribution of a positive variable, so the methodology embodied in hazard function analysis is applicable to any positively distributed variable.
The nature of living things and real machines is such that lifetimes (or other time-related events) often lead to rather simple, low-order distributions. For this reason, we have believed that low-order, parametric characterization of the distribution can be accomplished.
The parametric approach taken in the hazard procedures developed in the early 1980s at the University of Alabama at Birmingham was a decompositional approach. The distribution of intervals is viewed as consisting of one or more overlapping "phases" (herein called early, constant, and late) additive in hazard (competing risks). A generic functional form is utilized for the phases that can be simplified into a large number of hierarchically nested forms.
Each phase is scaled by a log-linear function of concomitant information. This allows the model to be non-proportional in hazards, an assumption often made, but often unrealistic.
Finally, the hazard model has been enriched in 3 ways. Because the intervals may not be known completely (incomplete, censored data), right censoring, left censoring, and interval censoring has been incorporated into the procedure. Second, the events considered may be repeating. This automatically accommodates a wide class of time-varying co-variables, that class that can be considered to change at specific intervals. Third, the event may be weighted on a positive scale (such as cost). Thus, the procedure, at its most complex, can accommodate time-related repeating cost data, with time-varying co-variables, and a non-proportional hazard structure.
For questions or comments, please contact us at firstname.lastname@example.org
- DIAGNOSIS: Epilepsy
- When Designing a Cancer Facility, Patient Outcomes Come First
- Hip Resurfacing: Still A Highly Competitive Option for the Younger Patient
- Introducing Cleveland Clinic’s Sports Cardiology Center
- INSPIRE: A New Option For Your Patients with OPSA
A Conversation with Imad Najm, MD, Director, Cleveland Clinic's Epilepsy Center
When it comes to epilepsy, many patients see primary care physicians (PCPs) and receive appropriate care. But sometimes, a patient needs to see a doctor who specializes in epilepsy treatment. That’s where Cleveland Clinic's Epilepsy Center can help.
“There is a need for a thorough evaluation for suspected seizures,” says Imad Najm, MD, Director of the Epilepsy Center. “It is very appropriate for the PCP to decide there is need for further workup.”
When should PCPs refer patients to the epilepsy center?
If the PCP feels comfortable with the treatment, he or she can continue care. If there are any lesions on the brain shown on a high-resolution MRI, it is appropriate to refer the patient to a neurologist. If the patient does not respond to one or more appropriately chosen anti-epileptic medications, we can comfortably advise the PCP to recommend that the patient see an epilepsy specialist.
What does it mean if an anti-epileptic medication fails to control the patient’s seizures?
If a patient fails anti-epileptic medication(s), one possibility is that the patient may not have epilepsy. In these cases, the diagnosis of pseudo seizures or non-epileptic seizures may be made and an appropriate treatment protocol implemented.
The second possibility is that the patient has epilepsy, but it is “pharmacoresistant.”
The recommendation is for the patient to be admitted to the epilepsy monitoring unit (EMU), where valuable electroencephalography (EEG) and video/semiological data regarding the seizure(s) are acquired. This evaluation will accomplish a key goal: to confirm the diagnosis of epilepsy or rule it out.
If an epilepsy diagnosis is confirmed, we next determine if the epilepsy is coming from a single, well-defined area of the brain. We find out if this patient has focal epilepsy that can be targeted with surgery. In such situations, surgery is effective for controlling seizures completely in 60 to 80 percent of the patients.
What can your patient expect during an initial visit?
During an initial evaluation, a detailed history is taken, including information regarding the type of feeling experienced before seizures (so-called auras) and what type of behavior is exhibited during a seizure. Any tests done (including MRI and EEG) to date will also be reviewed.
Our multidisciplinary team will then meet in a group setting to map out the most appropriate treatment plan, considering both medical and surgical options.
What options are there for epilepsy that doesn’t respond to medications?
Today, we have more options than ever before. Sometimes, implanting a vagus nerve stimulation device helps control seizures — in particular, for patients who have seizures activity in areas that are too critical to functioning to risk surgery.
Another possible and exciting option is switching patients (in particular children) to a ketogenic diet or a modified Atkins diet (high fat, low carbohydrate, adequate protein). About half of the patients on this diet have more than a 50 percent reduction in the number of seizures; 20 to 30 percent may have more than a 90 percent reduction in seizures. Less than 10 percent of patients on the ketogenic diet may have no seizures at all.
To refer a patient to Cleveland Clinic’s Epilepsy Center, call 855.REFER.123.
When Cleveland Clinic’s 377,000-square-foot cancer building opens in 2017, several things will be apparent on the surface: the flow of patients, the abundance of natural light and the presence of support services mixed in with clinical care.
If physicians and patients look deeper, though, they will find a facility designed expressly to improve patient outcomes through a collaborative, disease site-specific approach to cancer care.
The idea: Patients benefit from their oncologists, surgeons, radiation oncologists, social workers and other team members working together in proximity. They also benefit from having an infusion suite close to their doctor’s clinic, negating the need for multiple appointments and — along with many other such efficiencies — ultimately bringing healthcare costs down.
Such cancer care is already the norm in practice at Cleveland Clinic, but care being scattered in multiple locations across campus presents challenges, both for practitioners and for patients. The new multidisciplinary cancer building aims to bring it under one roof.
New Building Highlights
- $276 million Project cost
- 377,000 Square feet
- 7 Stories
- 126 Exam rooms
- 98 Chemo infusion rooms
Between East 102nd and East 105th streets
William Rawn Associates
“The new cancer building will allow us to centralize the cancer care we provide, creating a seamless, personalized experience for patients,” says Brian J. Bolwell, MD, Chairman of Cleveland Clinic’s Taussig Cancer Institute. Improving outcomes and designing clear care paths — customized by specific disease states — are both major goals.
Multidisciplinary work has existed for years, but the focus of organizing multidisciplinary groups by disease — teams focused around breast cancer, head and neck cancer, and other specific cancer types — will receive new emphasis in the facility.
Each disease group will have its own dedicated clinical practice area on a floor of the new facility, where a patient’s physician is mere steps away from a private or semiprivate treatment room. Likewise, each practice area will include space for subspecialized nurses, social workers and other key team members, plus exam and procedure rooms. For example, even though this will be an outpatient facility with surgeries performed elsewhere, surgeons will have the space and equipment needed to perform consults with patients on-site.
Growth in patient care
Patient volume has increased in all disease groups, with growth as high as 35 percent for some groups in 2013. However, increased patient demand is far from the only reason behind the need for such a facility.
In addition to the clinical focus on disease groups, the new facility will expand existing patient services and improve the way they are delivered. For example, because genetic counseling improves patient outcomes, the facility will have space dedicated to this practice, as well as genetics and genomics testing.
The facility will offer a new, centralized home for existing high-level treatment technology, including six linear accelerators and a Gamma Knife® suite. It also will include additional space to expand tumor boards and link community locations into these discussions.
Beyond clinical services, the facility will house critical support needs services as registered dietitians, prosthetics, wig services and a spiritual center.
“Cancer patients are uniformly scared,” Dr. Bolwell said in a recent interview with Crain’s Cleveland Business. “We have to provide many different ways to help patients and their families deal with the medical aspect of their disease but also the psychological aspect.”
Accelerating Phase I Research
Enhanced space matters as much for researchers as it does for care teams, Dr. Bolwell notes. The new building will have space dedicated to Phase I, II and III clinical trials — with a special emphasis on supporting Phase I trials.
Patients enrolled in a Phase I trial will have access to a full clinical care team. Hosting such trials on-site not only provides added support for patients but also eliminates unnecessary travel to other locations, especially for those whose doctors are located at the facility. The goal, at least partly, is to ease the process for people who are willing to participate in this crucial undertaking.
As with clinical care, another goal is to bring full teams — including researchers, clinicians, technicians, pharmacists and others involved in any given trial — into a common space to ease access issues and help trials run more efficiently. Doing so ultimately will aid the goal of clinical trials and move treatments that prove effective forward, to the benefit of more patients.
To refer a patient to Taussig Cancer Institute, call 855.REFER.123.
The case for hip resurfacing Hip resurfacing has several appealing features for the younger patient with hip arthritis. First, considerable bone is preserved in the upper femur compared with traditional hip replacement. Millimeters, rather than inches, are removed. Second, loading of the upper femur is more normal, in that the body weight is applied to the top of the femur instead of down the stem to the interior of the upper thigh. As a result, the progressive bone redistribution that takes place for several years after hip replacement does not occur with hip resurfacing.
Together, these two factors result in much less proximal femoral bone loss after resurfacing than after hip replacement. Long stems and bone grafting are therefore not needed for revision of a resurfacing device. Resurfacing can be revised to a standard total hip.
Additionally, the large femoral head of a resurfacing makes dislocation — the principal reason for revision surgery, according to U.S. federal databases — quite rare. Leg length inequality, probably the second most common complaint following total hip replacement, is also rare with resurfacing.
The stability and normal loading of hip resurfacing allow patients to return to unrestricted activity within a year of the procedure. This includes running, jumping, impact sports, manual labor and other activities that are typically discouraged following total hip replacement.
Complications of hip resurfacing
Concerns have been raised about metal debris from the bearings used in hip resurfacing. High levels of metal debris can result in pain, inflammation, swelling, tissue necrosis and pseudotumors.
Most of the problems with metallosis have occurred using modular metal-on-metal total hip replacement (MOM THR), not resurfacing. Unfortunately, the large heads involved in these procedures exerted excessive torque on trunions designed to accommodate much smaller head diameters. Micromotion, fretting and corrosion resulted in high metal ion levels and, in some cases, pseudotumors. MOM THR is no longer performed at most centers, including Cleveland Clinic.
Resurfacing is not the same as MOM THR. There is no modularity and no trunion. The risk of pseudotumor is 0.1 to 0.3 percent. In resurfacing, only three scenarios can result in excessive metallosis:
- A poorly designed resurfacing device. Several devices are no longer on the market. Today, the Birmingham Hip Resurfacing (BHR) device is the only FDA-approved resurfacing device available in the U.S. It has had the longest and best track record.
- Component malposition. Malposition of the socket can lead to edge loading and high levels of metal debris.
- Poor patient selection. We have learned that hip resurfacing is most successful in large individuals, usually men, under age 65. It should be avoided in small females and in patients with avascular necrosis or hip dysplasia.
In the absence of one of these three scenarios, metal ion levels remain very low and do not seem to pose a health risk. In fact, after extensive adjustment for confounding factors, mortality rates are lower with resurfacing compared with total hip replacement, and the risk of malignancy appears to decrease following hip resurfacing compared with the risk in an age- and sex-matched population. Mechanical complications, such as femoral neck fracture or loosening, are unusual.
Outcomes speak for themselves
In registry data, results with the BHR have surpassed those with all other devices. Success rates in younger men who have undergone resurfacing with the BHR have been exceptionally good. Aseptic survivorship rates of 99 percent and 100 percent at 10 and 14 years, respectively, have been reported in males under age 50 from two large centers in the U.K. At Cleveland Clinic, our survivorship rate for this challenging group is 100 percent.
In the series of the BHR designing surgeon (Derek McMinn, MD, FRCS), the success rate at 15 years was 98 percent in males and 92 percent in females, including all ages and diagnoses.
At Cleveland Clinic, we have performed more than 2,000 BHR procedures. The average patient age has been 53 (range, 14 to 84); 73 percent of patients have been male. We have had two femoral neck fractures, two cases of late femoral head collapse and two instances of metallosis (one in a small dysplastic female, one from socket malposition). Neither patient with metallosis developed a destructive pseudotumor. Additional imaging, such as CT scans for femoral anteversion and standing lateral hip X-rays for pelvic tilt, aid in patient selection. Our overall success rate is over 99 percent at up to eight years.
The bottom line
Hip resurfacing can provide excellent outcomes in properly selected patients when accurate technique and a well-designed implant are used. In the absence of one or more of these factors, metallosis may occur. Resurfacing allows full activity to be restored for the younger, active patient, and revision options are favorable.
Dr. Brooks is a staff physician in the Center for Adult Reconstruction in the Department of Orthopaedic Surgery and Chief of Surgery at Cleveland Clinic’s Euclid Hospital. He can be contacted at email@example.com or 216.444.4284.
To refer patients to our Department of Orthopaedic Surgery to determine if they are candidates for hip resurfacing, please call 855.REFER.123.
Disclosure: Dr. Brooks reports that he is a consultant for Stryker and for Smith & Nephew.
Multidisciplinary Care for Patients of All Ages
An ultramarathoner visits her primary care doctor for a regular checkup. She has a family history of early coronary disease and is concerned about her heart health. Her doctor orders an EKG, and when the results return, it appears abnormal. What should the doctor do? The physician would likely recommend further investigation and possible treatment and advise her to stop running to prevent an adverse cardiac event.
“The 'athlete’s heart' is a term used to describe the structural and electrical cardiac adaptations that occur with habitual, intensive training,” explains Dermot Phelan, MD, PhD. “Sometimes it can be very difficult to differentiate between an athlete’s heart and pathology.”
Why specialized heart care for athletes?
To accommodate athletes’ need for specialized care, Cleveland Clinic recently established a Sports Cardiology Center /services/heart/departments-centers/sports-cardiology-center . The multidisciplinary team consists of cardiologists from varying subspecialties, cardiothoracic surgeons, pulmonologists, sports medicine physicians, dietitians, sports psychologists and sports physiologists. Together, they assess athletes’ cardiovascular needs with the intention of allowing the athletes to continue to participate in the sports they love in a safe manner.
In recent years, sports participation has increased dramatically in the United States. The American College of Cardiology recognized the challenges inherent in managing the cardiovascular care of athletes by establishing the Section of Sports and Exercise Cardiology in 2011.
“The reason these types of centers are important is that athletes present unique cardiac problems to physicians, and, while many cardiologists will occasionally treat athletes, athletes usually make up a tiny portion of their practice. If there is concern, they determine the safest course of action is to disqualify the athlete. But frequently this is not appropriate. Alternatively, structural changes are attributed to athlete’s heart when in fact they do represent pathology,” says Dr. Phelan, who serves as Director of the new center.
Subspecialists understand that the cardiac needs of athletes differ from those of average patients. Take the marathon runner — it’s likely that her heart has undergone normal structural and electrical changes for her sport. Endurance training results in increased cardiac chamber volumes, resulting in increased stroke volume. At rest, her heart rate is slow as she can maintain her cardiac output with high stroke volume. Different sporting activities will result in different cardiac adaptations; an NFL linebacker’s heart will look very different from our marathon runner's. Strength training will result in hypertrophy of the heart muscle. Cardiac adaptations are also race- and sex-specific.
To the cardiologist accustomed to treating pathologies, thicker heart muscles will suggest hypertrophic cardiomyopathy, the most common cause of sudden cardiac death in athletes. A physician without experience in treating this patient population may suggest restricted activity, meaning the linebacker must give up his workout routine.
Helping athletes stay active
Some athletes shy away from seeing a physician because they are afraid of being told they can no longer perform. The Sports Cardiology team members are all sports participants or fans themselves and understand the value athletes place on their activity, whether it is a passionate pastime or their career.
“People fear that either they are going to be told to stop or that they are going to be restricted, and as a result they ignore symptoms. Unfortunately, that can oftentimes happen — they are being restricted and stopped inappropriately,” Dr. Phelan says. “We try to get as many athletes as possible back to training but in a safe manner.”
To provide the best treatment for athletes of any age, the team meets regularly to discuss cases.
“We try to tailor the evaluation and treatment to the athletes and their individual sports. For example, performing a traditional stress test designed to evaluate older people with coronary disease may not be the test of choice in a young ultramarathon runner,” Dr. Phelan says.
If an athlete has hypertension, many cardiologists would prescribe diuretics, a common treatment for high blood pressure. But some professional sports organizations consider these to be performance-enhancing drugs, and suddenly a legitimate treatment can impact an athlete’s ability to play. Other organizations ban beta-blockers. Our Sports Cardiology Center physicians understand which prescription drugs can’t be prescribed and which ones are better alternatives.
“Having this knowledge and understanding leads to better treatment,” Dr. Phelan says.
Care for athletes of all ages
Many people assume that “athlete” means college-aged and young adult patients. But Dr. Phelan stresses that the center sees many athletes who started their athletic careers late in life. These athletes frequently suffer from traditional cardiac problems, such as coronary artery disease.
“People who have lived a pretty unhealthy life and take up marathon running often think that is going to obviate the risk. While the benefits of regular exercise for one's heart health cannot be overstated and it is never too late to start, it does not wipe the slate clean. It is a good idea for people who have risk factors for coronary disease or symptoms such as shortness of breath, chest pain, lightheadedness or syncope with exercise to be evaluated prior to beginning intensive training regimens,” he says.
The experts at the Sports Cardiology Center will do their best to keep athletes of all ages — from novice to weekend warrior to pro athlete — performing.
To refer a patient to the Sports Cardiology Center, call 800.659.7822.
Obstructive sleep apnea (OSA) is a common disease affecting 18 million Americans that can be effectively treated with the first-line therapy, continuous positive airway pressure (CPAP). Yet according to studies, including a randomized controlled trial of 1,500 participants and a Cleveland Clinic study of 648 patients diagnosed with OSA, less than half of people with OSA are compliant with CPAP therapy.
This has made OSA a disease in need of a new treatment option. If untreated, patients with moderate to severe OSA are “chronically sleep deprived, fall asleep in social situations, have cognitive impairment and put a tremendous burden on their heart every night,” says Douglas Trask, MD, PhD, an otolaryngologist at Cleveland Clinic’s Head & Neck Institute.
In April 2014, a new treatment for OSA, Inspire® Upper Airway Stimulation, was approved by the FDA. Inspire therapy is the first implantable neurostimulation technology designed to address airway obstructions. “Inspire therapy offers a new and different approach to this problem by working with the natural physiology of the patient,” says Dr. Trask.
How it works
The Inspire therapy system consists of three implantable components: a programmable neurostimulator, a stimulation lead that delivers mild stimulation to the hypoglossal nerve, and a pressure-sensing lead that detects respiration. Controlled by a handheld device, the system senses breathing patterns and prompts the hypoglossal nerve to move the tongue forward so that the patient’s airway stays open when it needs to. “Since there are so many people who aren’t using CPAP, we are undertreating OSA patients. Inspire therapy is a very exciting breakthrough resulting from a lot of scientific work that provides another tool to treat our patients,” says Cleveland Clinic otolaryngologist Alan Kominsky, MD.
Implanting the system
The Inspire system is implanted during an outpatient procedure under general anesthesia. Three incisions — below the jaw, under the collarbone and under the pectoralis muscle — are made to implant the three components. Unlike traditional surgical options, the Inspire therapy procedure does not involve cutting or rearranging the tissues in the throat or jaw. “Many patients don’t choose traditional surgery because of the pain and time of recovery involved. This is a whole different class of surgery. But they aren’t mutually exclusive; traditional surgery will still be indicated for certain patients, such as those with large tonsils obstructing the airway,” says Dr. Kominsky.
Patient selection and follow-up
Inspire therapy is indicated for patients who are 22 and older, have CPAP intolerance, have a body mass index of 32 or less, and moderate to severe OSA with an index of 20 to 65. Their apneas have to be mostly obstructive. “Most people with OSA have multilevel obstruction: in the nose or behind the palate or tongue. Inspire therapy was originally thought to mostly treat the back of the tongue, but in practice it provides retropalatal improvement as well,” says Dr. Trask.
Patients undergo a sleep study before the procedure to ensure they qualify and after to titrate the device so that it provides stimulation that opens the airway without waking the patient.
Clinical data confirm efficacy
The results of a major trial of Inspire therapy, Stimulation Therapy for Apnea Reduction (STAR), were published January 2014 in the New England Journal of Medicine, which paved the way for the device's approval. In the prospective, 22-center trial, 126 patients with moderate to severe OSA who were implanted with the Inspire system were followed for 12 months. Patients showed a significant decrease in the apnea-hypopnea index (AHI) and oxygen desaturation index (ODI): AHI scores decreased by 68 percent and ODI by 70 percent. Quality of life measures also improved: Epworth Sleepiness Scale scores decreased and Functional Outcomes of Sleep Questionnaire scores increased.
The device had a less than 1 percent serious adverse event rate; minor side effects such as tingling in the tongue can be easily addressed.
A multidisciplinary approach
At Cleveland Clinic’s Head & Neck Institute, a multidisciplinary team of sleep neurologists, otolaryngologists, pulmonologists and sleep medicine physicians work collaboratively to select appropriate patients for Inspire therapy and provide comprehensive care from preparation through long-term follow-up. Drs. Kominsky and Trask are among a select group of physicians nationwide who are board-certified in otolaryngology and sleep medicine. “We have a group of physicians who each bring a unique perspective to the problem and are looking for the best treatment option for the patient,” says Dr. Trask.
To refer a patient for Inspire therapy, call 855.REFER.123.