Patient CC schedules an appointment with his primary care physician because he has noticed that his heartbeat is irregular at times. Patient CC is 74 years of age and retired with a history of coronary artery disease, an MI (12 years prior), CABG surgery (11 years prior), and stents placed in his coronary arteries (two years prior). During the appointment, Patient CC explains that he exercises regularly and always monitors his pulse rate during and after exercising. Recently, he says, his pulse has started "skipping beats," sometimes a few and sometimes "a lot." Since he noticed the missed beats, Patient CC has been checking his pulse off and on when he gets up and when he is resting and has noted that it has been increasingly irregular. Physical examination is negative for any changes or new abnormal findings. A routine 12-lead ECG is performed and shows no changes from previous ECGs. Routine lab work is done, and all values returned within normal limits. The physician prescribes a 48-hour Holter monitoring test.

Rationale and comments: Patient CC appears to have a type of arrhythmia that occurs relatively frequently. Ambulatory ECG monitoring such as a Holter monitor can provide helpful information about the type of arrhythmia and its link to any symptoms that Patient CC is having.

Patient CC completes the 48-hour monitoring test. As requested, he maintained a diary of any symptoms and his activities. Analysis of the Holter monitoring data showed that Patient CC was experiencing frequent runs of nonsustained monomorphic VT. Patient CC is notified of the results and is admitted to a local hospital for further testing and evaluation.

Rationale and comments: Asymptomatic (or relatively asymptomatic) runs of nonsustained VT may develop in persons with ischemic heart disease. Patient CC has had a MI; the damage from the infarction creates conditions that predispose him to develop a re-entry VT, such as monomorphic VT. The onset nonsustained VT may be an indicator that Patient CC is experiencing more ischemia. Diagnostic tests to assess for the presence of reversible ischemia are often indicated.

Patient CC is admitted to a telemetry unit for continuous telemetry monitoring. Serial cardiac enzymes obtained at eight-hour intervals are negative. Serum electrolytes are obtained; Patient CC's potassium and magnesium levels are within normal limits. Given Patient CC's past history of coronary artery disease, bypass surgery, and stent placement for re-occlusion of one of his grafts, the decision is made to perform a left heart catheterization. His catheterization shows a reduced EF of 30%; the stent and previous bypass grafts were found to be open with no significant blockages.

Rationale and comments: Myocardial ischemia from inadequate blood flow to the myocardium may cause an increase in ventricular arrhythmias. If ischemia is present, the treatment of choice is restoration of blood flow through percutaneous coronary procedures or coronary artery bypass graft surgery. However, Patient CC is not experiencing myocardial ischemia. His increasing ectopy is probably related to the damage from his previous MI and his increasing heart failure.

Over a period of days, Patient CC's medications are adjusted to optimize his heart function and halt further ventricular remodeling and progression of his heart failure. Following accepted standards for heart failure management, Patient CC is placed on a beta blocker and an ACE inhibitor along with furosemide for diuresis and potassium for replenishment as needed[109,110]. Despite optimization of his medications, Patient CC continues to experience frequent runs of nonsustained VT.

Rationale and comments: For patients with heart failure, primary prevention of sudden cardiac death involves aggressive management of heart failure symptoms and disease progression.

The medical team decides to evaluate Patient CC for device therapy. Because he has significant heart failure, the team chooses to evaluate him for combination cardiac resynchronization therapy and ICD. A 12-lead ECG and echocardiogram show that Patient CC would benefit from resynchronization therapy in addition to the ICD.

Rationale and comments: Patient CC has risk factors for sudden cardiac death, including reduced left ventricular function, ischemic heart disease, the continued presence of PVCs, and episodes of nonsustained VT after CABG surgery. Electrophysiology is indicated to determine if he is at high risk. If he is, implantation of an ICD is indicated. Some patients with heart failure who require an ICD may benefit from cardiac resynchronization therapy as well. In cardiac resynchronization therapy, a biventricular pacemaker is implanted, leads are placed in the right and left ventricles, and the device is programmed to coordinate the contraction of the right and left ventricles to restore a more normal pattern of ventricular contraction. Re-synchronizing ventricular contraction has been shown to improve functional status.

The physician explains the proposed procedure to Patient CC and his wife, including the purpose of the test, its possible risks, and the different results that might be obtained. The physician also explains the purpose of a biventricular pacemaker/ICD, how it works, why it might be needed in Patient CC's case, and how it would be implanted. In addition, he provides Patient CC and his wife with written material as well as a video on device therapy provided by one of the ICD manufacturers for use in patient education. Patient CC is very anxious, and his wife questions the physician privately about whether the defibrillator "will really work." The physician spends time with Patient CC and his wife, answering their questions and listening to their concerns.

Rationale and comments: People who learn that they may have a life-threatening arrhythmia requiring the placement of an ICD are frequently very anxious and frightened and may express anger, frustration, denial, or other emotions. The patient and his family may have a lot of questions about whether the device is really necessary and whether it will actually work. This is a crisis time for Patient CC and his family. Taking time to listen to the patient's and family's concerns and providing basic information about an ICD and its function are appropriate in the preprocedure period.

Patient CC is taken to the electrophysiology lab. Monitoring catheters containing multiple electrodes are inserted into the venous system and advanced to the appropriate sites. Using an established protocol, programmed electrical stimulation is performed. Sustained monomorphic VT is induced. Based on the electrophysiologist's assessment of Patient CC's current and potential needs for pacing and defibrillation, a dual-chamber biventricular pacemaker/ICD is implanted. Following implantation, before Patient CC is returned to his room, the ICD is tested and found to respond appropriately and effectively to a life-threatening arrhythmia.

Rationale and follow-up: An approved indication for implantation of an ICD is the presence of inducible sustained VT in a person with coronary artery disease and a previous MI. The selection of a specific device is the responsibility of the individual implanting the device and is based on an assessment of the patient's current and potential needs for defibrillation therapy as well as for permanent pacing. A dual-chamber ICD provides sensing in both the atrium and the ventricle; the atrial-sensing capability facilitates its ability to recognize and differentiate between atrial and ventricular arrhythmias. ICD function is tested before the procedure is completed, while the patient is still sedated.

Patient CC is returned to the telemetry unit. His vital signs are monitored frequently, and the generator site under his left clavicle is checked for signs of swelling or bleeding. The bilateral femoral sites used for insertion of venous catheters for the electrophysiology test are monitored for signs of bleeding or hematoma formation. Patient CC is placed on continuous telemetry monitoring and remains in the hospital for an additional 48 hours. During this time, his vital signs are stable and he develops no complications from the procedures. Telemetry monitoring shows that he has occasional PVCs and some runs of monomorphic VT that are terminated by the programmed antitachycardia pacing.

Rationale and comments: ATP is used to terminate VT. A group of pacing stimuli is rapidly delivered to the heart through the pacing electrode at a rate faster than the rate of the VT to depolarize the site of the arrhythmia, thus terminating the re-entry cycle. Because ATP uses about the same amount of electrical energy as a permanent pacemaker, patients usually experience minimal sensation. Patients may notice a period of light-headedness or "fluttering" in the chest from the rapid rate of the VT.

Discharge education for Patient CC includes incision care, arm restrictions, safety measures, driving restrictions, and instructions regarding appropriate actions if the device fires. The importance of Patient CC keeping all scheduled follow-up appointments and adhering to prescribed therapy for the ongoing management of his ischemic heart disease is stressed. Patient CC and his wife are provided with information about a local support group for ICD recipients and their families and are given written information in addition to verbal instructions.

Rationale and comments: Keeping follow-up appointments is critical for persons with ICDs to permit assessment of device function, identification of any programming or device problems, and assessment of the status of the battery to permit timely replacement. The amount of information that people need following ICD implantation is considerable, and the short hospital stays associated with ICD implantation do not permit time to review all the necessary material. In addition, immediately following ICD implantation, patients and their families may still seem to be in a crisis situation; their ability to hear and remember detailed information may be lessened. Providing outside resources and written resources is very important. Education should be continued in outpatient settings when the patient returns for follow-up visits.

Patient DD is admitted via EMS to the emergency room of the local hospital. He reports that he has an ICD and that it has fired six to eight times over the last three to four days. A cardiologist experienced with electrophysiology interrogates the ICD and retrieves stored data on all detected arrhythmias and device therapy delivered. The interrogation confirms that the patient has received a total of six shocks over a period of 72 hours for polymorphic VT and ventricular fibrillation. In two instances, multiple shocks were required to terminate the arrhythmia. Patient DD is diagnosed with "ICD storm."

Rationale and comments: When a patient reports multiple discharges from an ICD, the ICD should be interrogated to determine if the shocks actually occurred as the patient reported and if the shocks were delivered correctly (i.e., did the device correctly detect the arrhythmia and deliver therapy appropriately). Shocks that the patient reports feeling but that do not appear in stored data when the device is interrogated are sometimes referred to as "phantom shocks." Both counseling and measures to reduce anxiety may be effective in reducing the patient's sensation of phantom shocks. Shocks that are delivered inappropriately may reflect programming issues or equipment problems. Multiple shocks that are delivered over a short period for detected VT/ventricular fibrillation reflect appropriate ICD function; the condition is referred to as ICD or electrical storm.

A history and physical are performed. Patient DD is assessed for symptoms of recurrent ischemia or exacerbation of congestive heart failure. A 12-lead ECG is ordered along with an electrolyte panel and cardiac enzymes. A list of Patient DD's current medications is obtained, and Patient DD's adherence to his prescribed medications is evaluated.

Rationale and comments: In a person with an ICD and known ischemic heart disease, recurrent arrhythmias requiring ICD therapy may be triggered by changes in the patient's status, including recurrent or worsening ischemia and decompensated congestive heart failure. Indications of ischemia may include elevated cardiac enzymes and identifiable changes on an ECG from the patient's previous ECG. Indications of decompensated failure may include rales in the lung fields, edema in dependent sites, pulmonary edema present on chest x-ray, obvious weight gain, hypotension, report of diminished activity tolerance, dyspnea, and reduced oxygen saturation. Lack of adherence to prescribed antiarrhythmic therapy may cause an increase in arrhythmic episodes. In addition, failure to follow prescribed therapy for congestive heart failure or ischemic heart disease may result in recurrent ischemia or a congestive heart failure exacerbation.

Patient DD is admitted to an inpatient telemetry monitoring unit for further assessment, evaluation, and management. The 12-lead ECG shows no new changes, and his cardiac enzymes are negative. His serum electrolytes show slightly decreased serum potassium and serum magnesium levels. A chest x-ray shows mild signs of pulmonary edema. Patient DD denies any decrease in activity tolerance or other subjective symptoms of decompensated heart failure but does admit that the swelling in his ankles has gotten "a little worse." Patient DD's pre-admission medications are continued; these include digoxin, an ACE inhibitor, and a beta blocker for management of his heart failure and ischemic heart disease along with low-dose amiodarone for suppression of episodes of VT/ventricular fibrillation. The physician places Patient DD on IV diuretic therapy (instead of the patient's usual oral dose) for a brief period and restricts his fluid limit to 1,500 mL/day. Doses of his medications are adjusted, and consideration is given to adding an angiotensin receptor blocker in addition to Patient DD's other medications. Supplemental potassium and magnesium are ordered to restore Patient DD's serum levels to normal.

Rationale and comments: Appropriate initial intervention for ICD storm includes evaluating the efficacy of measures to control heart failure and ischemic heart disease. Correction of underlying electrolyte abnormalities, especially potassium and magnesium imbalances, is also important in decreasing the risk that the patient will develop recurrent arrhythmias.

With IV diuretic therapy and adjustments to his medications, Patient DD's signs of heart failure resolve. His activity tolerance improves, his chest x-ray is clear, and the swelling in his feet and ankles diminishes. As Patient DD and his family talk about his probable discharge one afternoon, Patient DD suddenly loses consciousness and slumps forward in his chair. Simultaneously, the ventricular fibrillation lethal arrhythmia alarm sounds at the central monitor station. Responding to the emergency, the staff note that Patient DD is unresponsive and without palpable pulse. Patient DD's ICD delivers a high-energy shock; the energy spike is noted on telemetry. The staff in Patient DD's room note seizure-like movement of his body. Patient DD does not wake up, and the monitor shows that he is remaining in ventricular fibrillation. As the staff begins to prepare to return Patient DD to bed in anticipation for the need for external defibrillation, the ICD fires a second time, terminating the arrhythmia and restoring a normal, perfusing rhythm. Patient DD is placed on a lidocaine drip and transferred to an intermediate coronary care unit.

Rationale and comments:People with ICDs who go into ventricular fibrillation may lose consciousness from the absence of a perfusing rhythm before the ICD has time to fire. Multiple ICD discharges for a single event of arrhythmia do not indicate a problem with ICD function. ICD programming includes a monitoring function. Once the ICD has fired, it monitors the patient's response. If the patient remains in ventricular fibrillation, the ICD is programmed to deliver another shock rapidly to terminate the rhythm. Depending on the programming, an ICD can deliver at least three shocks to terminate ventricular fibrillation. In the event that an ICD does not terminate a ventricular arrhythmia, external defibrillation may be performed. The defibrillator pads/paddles should not be applied directly over the ICD generator site. Lidocaine is an appropriate medication to use for continued suppression of ventricular arrhythmias after ventricular fibrillation has been terminated. The usual rate of infusion is 2–4 mg/min.

Patient DD remains on the lidocaine infusion for several days. His oral amiodarone dose is increased. He is evaluated for the presence of active myocardial ischemia, but cardiac catheterization shows no areas of reversible ischemia. Following discontinuation of his lidocaine drip, Patient DD is transferred back to a general telemetry unit for monitoring. Telemetry monitoring shows no additional episodes of ventricular fibrillation, and Patient DD's overall status remains stable. However, because his amiodarone dose has been significantly increased, the physicians decide to test his ICD to make sure that the defibrillation threshold has not been altered by the increased medication. Patient DD is taken to the electrophysiology lab, where he is sedated. Ventricular fibrillation is induced, the arrhythmia is detected, and his ICD fires, terminating the arrhythmia. Patient DD is returned to the telemetry unit and is discharged on the following day.

Rationale and comments: Increasing the dose of an antiarrhythmic medication or adding additional antiarrhythmic medications can change the amount of energy the defibrillator must deliver to the myocardium in order to defibrillate the heart. ICD testing is a useful procedure that can be performed in the electrophysiology lab. Because high-energy shocks are painful, patients are sedated for this procedure. Adjustments in programming can be made noninvasively if indicated by the results of the testing procedure.