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Apparatuses and methods for performing minimally invasive diagnostic and surgical procedures inside of a beating heart

Apparatuses and methods for performing minimally invasive diagnostic and surgical procedures inside of a beating heart description/claims

This application claims the benefit of U.S. Provisional Application No. 60/212,075, filed Jun. 20, 2000, incorporated by reference herein in its entirety.

The present invention relates generally to an apparatuses and methods for performing minimally invasive diagnostic and surgical procedures inside of a beating heart. More particularly, the present invention relates to an apparatuses and methods for accessing the heart chamber and performing minimally invasive diagnostic and surgical procedures, including diagnosing and repairing pathology of the heart valves (aortic, mitral, pulmonary and tricuspid) and the cardiac chambers (atrial and ventricular septums), inside of a heart while the heart is still beating.

Diagnostic and reparative surgical procedures have been performed on the heart since at least the 1920s. The first attempts at repairing heart valves began in 1923 with Cutler and Levine performing blind dilations of the mitral valve with cutting instruments. These dilations were blind in that the patient's blood blocked the surgeon's sight to the valve. Thereafter, Sutar reported a successful dilation of a stenotic, or narrowed, mitral valve by inserting his finger through the atrium across the valve. The technique of digital dilation was improved and championed by Harken in 1948 and Bailey in 1949. Later, more effective instruments were developed, such the Tubbs dilator, which can be placed through a purse-string suture in either the atrium or the ventricle, passed across the valve, and dilated. These various techniques were somewhat effective to repair heart valves, but operating “blind” made precision impossible, and dilation often tore the valve, leading to valvular insufficiency. In addition, embolic brain and other organ injuries occurred due to air entering the heart chambers and to loosening calcific debris.

The field of cardiac valve surgery did not develop significantly further until introduction, by Gibbon (1953) and by Lillehei and Kirklin (1955), of the heart-lung machine and cardiopulmonary bypass technique (CPB). With the body fully supported by CPB, the heart could be stopped with a protective cold blood potassium solution (cardioplegia) and opened, and more precise valve repairs and replacements could be performed under direct vision. At present, approximately 130,000 to 150,000 mitral valve procedures are performed annually. (1). All require full CPB, cardiac arrest, and a thoracic incision.

The repair of septal defects, i.e., holes in the walls of the cardiac chambers, followed a similar course. Several surgeons attempted to repair atrial septal defects in a beating heart by placing sutures blindly through the chamber walls or by working through atrial wells. These “wells” were created by “dams” sewn into the atrium. Once the well was constructed, the heart chamber was opened. The blood would rise a few centimeters up the walls of the well, due the pressure in the heart chamber. The relatively low pressure in the atrium, ranging from 2-20 mmHg, kept the blood from rising more than a few centimeters. The repair then was performed through the well.

Like the valve repairs, this procedure was a blind one, due to the surgeon's inability to see through blood that collected in the heart chamber. In addition, blood loss was unpredictable. Further, it was easy to entrain air into the cardiac chamber during this procedure, which could cause heart failure, strokes, and death. Several creative methods were devised to temporarily stop blood flow or briefly turn off the circulation or to support the circulation using another person's circulatory system, but these methods were cumbersome and dangerous, and only the simplest repairs could be performed. Safe and effective chamber wall repairs did not truly begin until introduction of the heart lung machine. The heart-lung machine supported circulation so that the surgeon could repair the septal defect under direct vision.

With the advent of the heart-lung machine, CPB became the preferred method of cardiac surgery. The standard CPB procedure requires opening the chest, placing the patient on CPB, and stopping the heart with cardioplegia. The heart itself is then opened and repaired. Heart valves replaced or repaired by various techniques, and defects in the atrial and ventricular septums can be sutured closed directly, or a patch can be sewn into place over the septum.

Despite advances, many open-heart surgical procedures still have a 5-9% mortality rate and a 20% morbidity rate. (2). In order to reduce morbidity, several “less invasive” approaches have been developed. Specialized clamps and cannulas allow the patient to be placed on CPB though smaller chest incisions or via a femoral approach. (3-8). Alterations in technique, new instruments, and the use of video have been utilized to further reduce incision size. (9). These advances improve patient satisfaction and may improve return-to-work rates. (6, 10).

The advances have not reduced the major complication rates, however, and they are associated with an increased risk of aortic dissection and stroke. Further, they increase the cost per case by approximately $5000. (8, 11). The major complication rate has not been reduced because the procedures have not eliminated the need for cardioplegia and CPB, which together account for the majority of the complications.

When the heart is stopped for surgery, it is cut off from its blood supply. Cardioplegia, administered by one of several techniques, can minimize heart injury. (12). However, cardiac function is always depressed after cardioplegic arrest, and the longer the duration of arrest, the greater the injury. (13). In addition to the risks associated with cardioplegia, CPB, in its own right, can be damaging in multiple ways. CPB causes bleeding by disrupting hemostasis (blood clotting). CPB consumes platelets, activates fibrinogen, generates fibrin split products, activates the contact activation system, and dilutes formed and plasma clotting elements. (14-17). CPB also elicits a substantial whole body inflammatory response and generates large numbers of vasoactive substances. (17-19). This leads to pulmonary dysfunction, third space loss, and neurohumoral imbalances. (17, 20). Additionally, CPB has negative effects on the immune system. (21). Furthermore, macroemboli produced during cannulation and aortic cross-clamping, as well as gaseous and particulate microemboli generated during the period of CPB, have been implicated in neurologic dysfunction seen frequently after open heart surgery. (22-24). A recent article in the New England Journal of Medicine reported that up to 6.1% of patients have adverse cerebral outcomes after cardiac surgery, with the majority of events attributable to CPB. (25).

Several approaches have been developed to perform coronary artery bypass grafting on the beating heart using stabilization technologies. (26). These approaches eliminate the need for cardioplegia and CPB, reducing morbidity and per case cost. (20). Surgery of the interior of the heart is not possible with these methods, however, because the methods do not allow the cardiac chambers to be opened. To do surgery on the heart without CPB, the heart must continue to beat. Opening the cardiac chambers of a beating heart would lead to massive blood loss and air being drawn into the circulation in large amounts. Additionally, in order to directly visualize the area of surgical interest, the cardiac chamber must be free of blood. This cannot occur while the heart is beating.

Cardiac surgery is undergoing a rapid evolution to less and less invasive procedures. Valve repairs and replacements can now be performed through significantly smaller incisions. Dr. Mehmet Oz at Columbia University has reported of a clip device that can be inserted through the apex of the left ventricle of the heart and clipped onto the leaflets of the mitral valve. (32). The clip effectively sews the anterior leaflet to the posterior leaflet. This clip technique mimics one type of mitral valve repair, called a “bow-tie” or Alfiori repair, and, as best understood, currently requires CPB. The clip technique has some potential drawbacks, however, including possible device embolization. In addition, entering the heart through the apex of the left ventricle increases the risk of blood loss due to the high intracavitary pressures of the ventricle and does not allow for any other work to be performed on the mitral valve.

The present invention is drawn to apparatuses and methods for performing minimally invasive diagnostic and surgical procedures inside of a beating heart that alleviate the need for cardiopulmonary bypass (CPB), minimizes the risk of air introduction into the heart during surgery and emboli, and maintains sufficient intracardial pressure during the diagnostic and surgical procedures. In addition, the apparatuses and methods are compatible with several types of diagnostic and surgical techniques, including mitral valve repair, repair of atrial or ventricular septal defects, endovascular aortic surgery, and electrophysiologic studies.

A cardiac port for insertion through a chamber wall of a heart chamber to perform a medical procedure inside of a beating heart in accordance with the invention includes a housing, at least one valve, and an inlet. The housing has a first end, a second end, and a lumen therethrough. The valve is disposed in the housing to open and close the lumen. The inlet is connected to the housing. The inlet has an inlet passage in fluid communication with the lumen of the housing. The inlet is adapted to transmit a fluid between an exterior of the port and the lumen of the housing.

In another arrangement of the invention, a cardiac port for insertion through a chamber wall of a heart chamber to perform a medical procedure inside of a beating heart includes a housing, at least one valve, and first and second retainer members. The housing has a first end, a second end, and a lumen therethrough. The valve is disposed in the housing to open and close the lumen. The first and second retainer members are located on the housing. The first retainer member is spaced from the second retainer member a predetermined distance to anchor the chamber wall between the first and second retainer members. The first and second retainer members can comprise first and second flanges disposed on an exterior surface of the housing.

In another aspect of the invention, an assembly for use in performing a medical procedure inside of a beating heart of a patient includes a port and a fluid transport device. The port in turn includes a housing having a first end, a second end, and a lumen therethrough; at least one valve disposed in the housing to open and close the lumen; and an inlet connected to the housing. The housing is configured for insertion through a chamber wall of a heart chamber so that the first end is exterior of the chamber wall and the second end is interior of the chamber wall. The inlet has an inlet passage in fluid communication with the lumen of the housing. The fluid transport device has one end that attaches to the inlet of the port, another end that attaches to a fluid source, and a fluid channel therebetween to pass a fluid from the fluid source to the inlet. The fluid passes from the inlet through the inlet passage and through the lumen into the heart chamber to maintain an intra-chamber pressure at a desired level.

A method of accessing an interior of a heart chamber of a heart in accordance with the invention comprises the steps of maintaining beating of the heart, and inserting a port in a chamber wall of the heart chamber, the port having a lumen therethrough for accessing the interior of the heart chamber from exterior of the heart chamber. The inserting step can comprise securing the port in an atrial wall to access an interior of the heart.

In still another aspect of the invention, a method of preparing a beating heart for a diagnostic or medical procedure comprises the steps of inserting a port in a chamber wall of the beating heart, the port having a lumen to access to the heart chamber; and pressurizing the heart chamber with blood from a patient's artery. The method can include positioning a cannula through the chamber wall, and the pressurizing step can be accomplished by shunting arterial blood from the patient's artery into the heart chamber via the cannula. In another arrangement, the pressurizing step can be accomplished by shunting arterial blood from the patient's artery into the heart chamber via the port.

• Provisional Patent
• Utility Patent

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